Trailing slash

* made haruploader tolerate url's with a trailing slash
* unit tests for above
* editied test_config.yaml and changed url's to a single URL pointed at example.com, so the acceptance test runs faster and doesn't access edx.org.

/cc @clytwynec @benpatterson @jzoldak  
good idea.
do you think we should merge this fix now, or wait until it's refactored and properly tested?
if we do merge, should I remove the tests, or just leave them as-is, with a TODO in the test code?