added zipWithNext and zipWithPreviousAndNext combinators
Merge pull request #210 from etorreborre/master

added zipWithNext and zipWithPreviousAndNext combinators
UTF8 -> UTF-8
Less precise types for `halt` and `empty`
Fix spelling of "supersede"
Fix compilation for Scala 2.11
Merge pull request #217 from radekm/fix-for-scala-2.11

Fix compilation for Scala 2.11
Merge pull request #216 from radekm/less-precise-types-halt-empty

Less precise types for `halt` and `empty`
Scaladocs on empty
Allow type parameters to empty