Merge pull request #23 from ricemery/binary

Add binary exercise
Added roman-numerals exercise
Merge pull request #24 from ErikSchierboom/roman-numerals

Added roman-numerals exercise.

Thanks
Add prime-factors exercise
Merge pull request #25 from ricemery/prime-factors

Add prime-factors exercise
Simplify example
Merge branch 'master' of https://github.com/exercism/xscala into rna-transcription
Merge pull request #26 from ricemery/rna-transcription

Rna transcription
Added raindrops exercise
Added raindrops exercise
Merge pull request #27 from ricemery/raindrops

Raindrops exercise
allergies exercise
Merge pull request #28 from ricemery/allergies

allergies exercise
Clean up error handling in Binary example. Add additional test cases