A bunch of fixes and minor refactor

[bcat-eu]

Fixed many smaller errors to make it work with newer versions of Erlang, Elixir and Phoenix (it didn't in my case):

• Erlang/OTP 19
• Elixir 1.3.3
• Phoenix 1.2

refactored few functions to silence warnings.

Tests are green, testing per hand looks good though I wasn't really thorough.