Switch to Specs 2 rather than ScalaTest

The matchers seem a bit more extensive to me (eg traverseables) and
I'm just a bit more used to working with Specs 2.
Update to Scala 2.10.1

http://www.scala-lang.org/2.10.1
Rich-treewalks & TreeFilters

Implementing map, foreach, & withFilter lets you treat TreeWalks like
an iterator in for-comprehensions, even though they don't quite fit the
next()/hasNext() interface required.