Initial tests for dependency resolving

- Reworked the helpers for existing suites and expanded them
- Created a mock git resource module to test for its dependency fetching
- Added a test suite for dependency resolving with first checks for
  common cases (https://gist.github.com/ferd/197cc5c0b85aae370436)

Left to do would include:

- Verify warnings
- Verify failures
- Verify dependency updates resolving

API for Plugins (solves #22)

Profiles

- includes logging macros and turns them to functions
- exports customized types

properly escape paths

Transform rebar3 ct input

verbosity. Verbosity can be a integer but I am
parsing it as a term. This will work for integers
as well as terms.

command line by converting things to atoms and
splitting up strings where needed.

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