SPARK-1316. Remove use of Commons IO

Commons IO is actually barely used, and is not a declared dependency. This just replaces with equivalents from the JDK and Guava.

Author: Sean Owen <sowen@cloudera.com>

Closes #1173 from srowen/SPARK-1316 and squashes the following commits:

2eb53db [Sean Owen] Reorder Guava import
8fde404 [Sean Owen] Remove use of Commons IO, which is not actually a dependency