Make elixir tests run with example if flag is given

This is useful for testing the tests when new versions of Elixir come out.
Make Elixir examples/tests work with 0.11.0 - 0.12.2

This basically adds a bunch of workarounds for Elixir's very fast
deprecation cycle.
Merge pull request #1306 from pminten/elixir-compatibility-fixes

Elixir compatibility fixes (supports 0.11.0 - 0.12.2)