Merge pull request #220 from etsy/develop

A few more small changes from Etsy
make an implicit explicit
Bump version to 0.8.1
Merge branch 'release/0.8.1'
Merge branch 'release/0.8.1' into develop
Fix README version
Merge branch 'develop'
Updates to 0.8.2-SNAPSHOT
Added combinations(n,k) to RichPipe
Fixed bug in combinations(n,k)
Fixed read bug in combinations(n,k)
Moved combinations out of RichPipe to mathematics package, added permutations
Using IndexedSeq as opposed to Array, as per Oscar
change Source.write to Source.writeFrom
Merge pull request #223 from avibryant/writeFrom

change Source.write to Source.writeFrom
Added functionality to generate tuples with repititions that satisfy some predicate
Changes as per Oscar
Simplified permutations & combinations logic
Clarify takeWhile's behavior in documentation.
Merge pull request #227 from arkajit/develop

Clarify takeWhile's behavior in documentation.