Phoenix compilation failing on ":plug" dependency

[knewmanTE]

Doing a Phoenix run, I'm seeing it exit out with the following error:

Setup phoenix: == Compilation error on file lib/plug/crypto/message_encryptor.ex ==
Setup phoenix: ** (CompileError) lib/plug/crypto/message_encryptor.ex:307: function '<-'/2 undefined
Setup phoenix:     (stdlib) lists.erl:1337: :lists.foreach/2
Setup phoenix:     (stdlib) erl_eval.erl:669: :erl_eval.do_apply/6
Setup phoenix: 
Setup phoenix: could not compile dependency :plug, "mix compile" failed. You can recompile this dependency with "mix deps.compile plug", update it with "mix deps.update plug" or clean it with "mix deps.clean plug"

[stevedomin]

Not sure if that would solve the issue but all the Elixir dependencies are in need of a serious upgrade (Elixir 1.1 -> 1.3, Phoenix 1.0.2 -> 1.2.1, etc.)

Happy to put a PR in if that helps?

[knewmanTE]

@stevedomin that would be great!

[ckampfe]

noting this here for future reference: #2214

[LadyMozzarella]

See #2214