Return invalid options as strings
Fix example for exception/1
Merge pull request #2315 from chyndman/gsoc-windows

Mix.CLITest: explicitly declare environment variables (Windows-friendly)
Merge pull request #2317 from vicmargar/fix-exception-doc

Fix doc example for exception/1
\d is a printable character
Merge pull request #2312 from alco/option-parser-fixes

Return invalid options as strings
Update CHANGELOG, fix tests and typespecs
Exit with proper test code on test_erlang, closes #2313