A little bit of everything

This PR does lots of things:

Remove /doc and gitignore it
Refactor Raygun functions to not spawn unmonitored processes and simply wait for the response of Raygun. Also returns :ok or {:error, reason} tuple so the user may identify what's happening
Add meck as test dependency
Add one test for Raygun.Format
Add one test for Raygun
Update deps
Remove exrm as it doesn't depend on it (Fixes https://github.com/Cobenian/raygun/issues/11)

Cobenian / raygun