Add a 'lines' combinator to the text package. Associated with PR #190

Suggested by @fthomas in association with proposed NIO based filesystem tools implemented in PR #190.

The lines: Process1[String, String] combinator will take a stream of Strings and repartition them by line endings. The behavior is indended to be identical to that of scala.io.Source.getLines.
Add asynchronous nio versions of io file operations