Allow --app flag to be passed on mix new

  Allows path to not follow app name conventions
allow lowercase http(s)_proxy env var
Parse unary/binary operators regardless of number of spaces

closes #2534.
Added @doc false to handle call
Merge pull request #2582 from tomkadwill/added-doc-false

Added @doc false to handle_call functions
Merge pull request #2581 from mururu/parse-space

Parse unary/binary operators regardless of number of spaces
Merge pull request #2580 from Joe-noh/lowercase-http-s-proxy

[MIX] allow lowercase http(s)_proxy env var
Merge pull request #2556 from patrickgombert/master

Allow --app flag to be passed on mix new