Export configure_sink/2 for runtime sink config

Reviewed-by: macintux

Addresses #291. External consumers who use 'none'
as a level in their log messages will fail dialyzer.

Address #286. This will enable applications to
dynamically configure log sinks, provided they
have already instrumented the code via parse
transformation to use those sinks.

Addresses #287

Update travis yml

Put the warning map value into process dictionary (Fix OTP 18 test failures)

Address #332: try both id and name

Leverage existing lager_app:get_env wrapper for error_logger_lager_h

Lager logs its own application start up message. Previously
this message was discarded or not received quickly enough
to cause test failures, but now it seems as though it
is being received and causing several test failures
even though we are explicitly flushing it away.

We introduce a 5 millisecond sleep for several tests
to make sure the start up message is received before the
flush command dumps it.

The sync_error_logger file looks up the value to send from a process
dictionary entry named `warning_map' When it is unset, it uses a mapping
which is fine for OTP 17 and before, but 18 and 19 the value changed.

So now we put the current mapping value into the process dictionary so
that the messages do not cause failed tests.

Previously, was always hardcoded to the default sink name.

Previously, configuration would come from application:get_env/3 or
proplists:get_value/3. Now we standardize on a single format
for retrieving values from the environment or from a proplist.

Port improper iolist support from io_lib_format.erl & add tests

Reviewed-by: macintux

Signed-off-by: Brian L. Troutwine <brian.troutwine@adroll.com>

Signed-off-by: Brian L. Troutwine <brian.troutwine@adroll.com>

This is, perhaps, not the most ideal setup. It still ignores other
sinks but does bring logging back online after the appropriate delay.

Signed-off-by: Brian L. Troutwine <brian.troutwine@adroll.com>

This test only passes when run in isolation. That is, if you run the
suite solo everything is beautiful and nothing hurts. When run in the
group, it fails. By inspection it seems that no trace messages are
being sent and this causes the failure, for want of specific traces.

Signed-off-by: Brian L. Troutwine <brian.troutwine@adroll.com>

At this point in the work, the killer will correctly stop the
DEFAULT_SINK in the event of overload but our friend never comes back
up and lager stops working past this point.

Oops!

Error message:

=SUPERVISOR REPORT==== 10-Mar-2016::16:18:11 ===
     Supervisor: {local,lager_handler_watcher_sup}
     Context:    child_terminated
     Reason:     killed
     Offender:   [{pid,<0.63.0>},
                  {id,lager_handler_watcher},
                  {mfargs,{lager_handler_watcher,start_link,undefined}},
                  {restart_type,temporary},
                  {shutdown,5000},
                  {child_type,worker}]

=SUPERVISOR REPORT==== 10-Mar-2016::16:18:11 ===
     Supervisor: {local,lager_handler_watcher_sup}
     Context:    child_terminated
     Reason:     killed
     Offender:   [{pid,<0.59.0>},
                  {id,lager_handler_watcher},
                  {mfargs,{lager_handler_watcher,start_link,undefined}},
                  {restart_type,temporary},
                  {shutdown,5000},
                  {child_type,worker}]

=PROGRESS REPORT==== 10-Mar-2016::16:18:11 ===
          supervisor: {local,lager_sup}
             started: [{pid,<0.113.0>},
                       {id,lager},
                       {mfargs,{gen_event,start_link,[{local,lager_event}]}},
                       {restart_type,permanent},
                       {shutdown,5000},
                       {child_type,worker}]

Signed-off-by: Brian L. Troutwine <brian@troutwine.us>

Signed-off-by: Brian L. Troutwine <brian@troutwine.us>

Otherwise `lager_transform` fails after de9012628a

The error message is:

    test/pr_nested_record_test.erl: error in parse transform 'lager_transform': {function_clause,
                                                 [{lager_transform,
                                                   '-walk_ast/2-fun-0-',
                                                   [{typed_record_field,
                                                     {record_field,5,
                                                      {atom,5,field1}},
                                                     {type,5,term,[]}}],
                                                   [{file,
                                                     "src/lager_transform.erl"},
                                                    {line,62}]},

API to explicitly call log rotation

Reviewed-by: macintux

Do not add logroot in expand_path sometimes

Reviewed-by: bsparrow435

Option to not reformat error_logger messages

Reviewed-by: macintux

If expand_path/1 already contains LogRoot in its RelPath, do not
add it again.

Close file right after rotation

Reviewed-by: bsparrow435