Setup elixir formatter

[olgad0110]

Setup elixir formatter for mix.exs file and all ex/exs files in config, lib, test directories
Adjust code to fomatter (by running mix format)

[olgad0110]

@nekath feel free to add any additional configuration to the formatter if you think it's necessary

[nekath]

I played a bit with formatter and importing setups from various libs like phoenix, ecto, plug.
There are a few problems at this moment

• some of the libs formatter file is added just in master
• currently there is a requirement to define every dependency in deps (dep from you import a rules), therefore we would need to add some libs to deps, i.e. using ecto is pulled by phoenix_ecto, so it would have to be added to deps.

Other option is to just copy-paste locals_without_parens definitions from above libs into our .formatter.exs and don't care for some time.

I'm for second option.
Nevertheless we should also add credo and run it as part of CI process :)

What do you think? :)

[olgad0110]

agree, let's go with second option