SPARK-1316. Remove use of Commons IO

(This follows from a side point on SPARK-1133, in discussion of the PR: https://github.com/apache/spark/pull/164 )

Commons IO is barely used in the project, and can easily be replaced with equivalent calls to Guava or the existing Spark `Utils.scala` class.

Removing a dependency feels good, and this one in particular can get a little problematic since Hadoop uses it too.