Merge pull request #3 from tomkowz/fork-master

Removed both redundant inheritance of CryptoHash enum and assigned values to cases
Update Byte extension for bits. Bool -> Bit
Bit.zero -> Bit.Zero (beta6)
Workaround for broken bitwise operations (rdar://18060945)
calculate() return non-optional value (#2)
Workaround against swift crash when return value as property Xcode6-beta6 rdar://18061554