Fix insufficiently general type signatures
Tidy up some comments
Run test suite on all available cores by default
Implemented lookupXX
`selector` replaced by `accept` in `lookupOrd`
Implemented `isSubmapOfBy`.
Implemented `isSubmapOf`.
Implemented `isProperSubmapOfBy`.
implemented `isProperSubmapOf`.
Mutual recursive implementation of isSubmapBy and isProperSubmapBy
Merge
Merge pull request #57 from kgeorgiy/isSubmap

Implemented isSubmap, isSubmapBy, isProperSubMap, isProperSubmapBy
Merge pull request #56 from kgeorgiy/lookupXX

Implemented lookupGE, lookupLT and lookupLE
Cleaning up trailing whitespace makes me cranky >:-(