update provider template for changes to format_error/1

fix plugin module template, add merl to escript, upgrade erlydtl

Drop search for templates in cwd

Templates should only be in ~/.rebar3/templates and the built-in ones,
bar some specific overrides someone may want.

Looking recursively for templates in the CWD (.) may end up searching
nearly forever if the project is being created at the top of a very deep
directory tree, with extremely unlikely chances to find relevant
templates.

It causes more problems than benefits.

Add Erlang R14B04 for Travis CI

Fix rebar dialyzer to work on applications in rebar archive

Fixes cases where dialyzer warning might include a `~` causing printing
to console to fail with `badarg`.

code:lib_dir/1,2 can return archive directory for rebar escript archive
applications, rather than the application's directory in the project.

Add dependencies not listed in `applications` to `dialyzer_plt_apps`.

[WIP] Improve dialyzer command

Adds a base plt per OTP version that is stored in $HOME/.rebar3/. The
base plt is copied to new projects that don't have a plt for the active
OTP version. Modules are added/removed to the project's copy based on
the project's .app files.

* Add description
* Make configuration constitent (prefix with dialyzer_)
* Make printed info consistent

* --update-plt=true|false (false skips updating plt)
* --succ-typings=true|false (false skips success typing analysis)

Try to automatically detect all application dependencies when `plt_apps`
is not included in `rebar.config`.

Note that this will not follow `runtime_dependencies` in OTP
applications. This can be resolved by adding any missing
`runtime_dependencies` to `applications` in the .app.src file or
including `plt_apps` in `rebar.config`.

Strip ":0: " from unknown type/function/behaviour warnings

* Only include `plt_apps` (defaults to deps) in a single PLT
* Update PLT when `plt_apps` (or deps) are changed or updated
* Print warnings for all dialyzer runs (not just `succ_typings`)

* Nolonger supress standard warnings
* Nolonger include race_conditions by default[1]

[1] http://erlang.org/pipermail/erlang-bugs/2014-July/004518.html

fix callback r14 support

catch error on multiplpe app files in an app dir