Merge pull request #24 from garborg/master

Clean up getindex and find, remove calls to replaceNA
Fix convert methods for PDA's
comment out broken reference to DataFrame type
Fix #17
Merge pull request #27 from JuliaStats/kms/or_fix

Fix #17
Merge pull request #26 from StefanKarpinski/pull-request/a679f1eb

comment out broken reference to DataFrame type
Code cleanup
Remove dataint, datafloat, databool
Improve test coverage; fix allna bug
Fix #30, Dividing DataArray by integer gives InexactError()
Rename REQUIRES->REQUIRE and remove SortingAlgorithms dependency

As far as I can tell, we don't actually use SortingAlgorithms anywhere
in DataArrays (only DataFrames)
Fix unique and levels semantics
Remove values function
Add README
Fix bug in getindex type signature
Fix bug in datamatrix.jl

Add systematic test coverage
Add datavector tests