Upgrade to JUnit 4.11

Fix a conflict with Hamcrest matcher classes that was previously fixed
by classpath ordering. This brings JUnit's Hamcrest dependency up to
version 1.3, which is _more_ compatible with rest-driver's other
dependencies.

This should make using rest-driver (in particular the HasXPath matcher)
easier in Clojure.
Merge pull request #132 from joelittlejohn/junit411

Upgrade to JUnit 4.11