Support for Rebar3 style deps

[walrusVision]

Elvis fails on a rebar.config file which uses Rebar3 style deps with the following error.

# rebar.config [FAIL]
Error: 'function_clause' while applying rule 'protocol_for_deps_rebar'.
Loading files...
Applying rules...

This is the style which it fails on.

{deps, [
  {poolboy, {git, "https://github.com/devinus/poolboy.git", {tag, "1.5.1"}}},
  {gproc,   {git, "https://github.com/uwiger/gproc.git", {branch, "master"}}}
]
}.