Fix misprint in #130

Digest could mean HTTP Digest Authentication which is completely
different from what we call Digest currently. Renaming this is
essential to implement the actual HTTP Digest Authentication

Big commit. Switched algorithm to one which will favor
the connection with the smallest pipeline first
(deciding ties by timestamp of last finished request,
and then by pid as ultimate tie breaker).

Note: this also drastically changes the internal
representation of the connection in ets and is dependent
on specific order of operations when changing key values
to limit risk of race conditions between loadbalancer
and a given connection.

Also removed connection reporting of start of request
as this was no longer necessary since the load balancer
tees up the entry into ets with a 1.

Use of foldl for iteration is not hidden as implementation
detail.  Also hid details of how to message conn to set
tracing within API.

HTTP connection process now manages both scenarios
requiring cleaning up of the load balancer's ets table;
instead of this being owned by both the conn and lb.

Moved all interactions with ets table tracking
connections to API functions on ibrowse_lb,
to reduce knowledge of ets table and its structure.

Also fixed "bug" where ceiling for pipelining
threshold was different than the set value for increment;
made them the same.

Tracking size in http connection process state
was unnecessary as it wasn't queried for logic
or obvious reporting and ets table should have
right (within 1) value already.

For consistency, added macro aliases for remaining
ets table names to be found all in one place.

Supports HTTP and HTTPS destinations and performs all hostname
resolution via the SOCKS proxy, preventing privacy leakage if used
with Tor.

If hostname is a valid IP address then it is used directly, the
hostname is not resolved again via the SOCKS5 proxy (Patch suggested
by Klaus Trainer but implementation here slightly different).

This reverts commit d8150feeaf.

Conflicts:
	.gitignore
	src/ibrowse_http_client.erl
	src/ibrowse_socks5.erl

if the option return_raw_request` was unset or false, ibrowse was
still returning the returning thhe raw request. This change fix it.
(Spotted while running couchdb tests)

fix function_clause error:

        {error,
        {error,
            {'EXIT',
                {{function_clause,
                     [{ibrowse_http_client,do_send_body_1,
                          [{{ok,<<>>},

The case {Function, State} wasn't took in consideration while handling
the body.

in that place leads to silent termination, since client will never be
informed. Instead of crashing wait for tcp_closed and cleanup nicely.

Below are the warnings that were fixed by this commit.

[git: master]Iris:ibrowse andreas$ make dialyzer
Building local plt at .dialyzer_plt

dialyzer --output_plt .dialyzer_plt --build_plt \
	   --apps erts kernel stdlib ssl crypto public_key asn1 compiler hipe edoc gs syntax_tools inets xmerl runtime_tools mnesia
  Compiling some key modules to native code... done in 0m19.73s
  Creating PLT .dialyzer_plt ... done in 1m40.98s
done (passed successfully)
dialyzer --fullpath --plt .dialyzer_plt -Wrace_conditions -Wunmatched_returns -Werror_handling -r ./ebin
  Checking whether the PLT .dialyzer_plt is up-to-date... yes
  Proceeding with analysis...
src/ibrowse_http_client.erl:197: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:298: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:322: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:335: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:352: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:582: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:587: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:590: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:706: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:789: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:797: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:1402: Expression produces a value of type 'ok' | {'error',_}, but this value is unmatched
src/ibrowse_http_client.erl:1859: Expression produces a value of type 'ok' | integer(), but this value is unmatched
src/ibrowse_socks5.erl:25: Expression produces a value of type {'ok',<<_:16>>}, but this value is unmatched
 done in 0m8.07s
done (warnings were emitted)
make: *** [dialyzer] Error 2

When a tcp_closed or ssl_closed message is handled while ibrowse is
trying to send a request to a worker, ibrowse would incorrectly return a
req_timedout message, when, in fact, the request had not even been
handled.

This patch attempts to avoid that race condition by signalling tcp or
ssl closed messages back to ibrowse differently than a normal exit.

This should, for example, allow user to specify "TE: gzip" header in request and unzip response body manually.

Typically used to specify non-default, garbage collection options.

inet:gethostbyname/1 might fail for IPv6 literals, therefore check first
if host is an IPv6 address literal.