Fix broken links, fix travis

Summary:
Caught by travis.
https://travis-ci.org/Instagram/IGListKit/jobs/185367790

Many thanks to Sherlouk for setting this up. 💯
Closes #344

Differential Revision: D4351406

Pulled By: jessesquires

fbshipit-source-id: 385a3c5d738b1576a95812b9e4c598ea25773a78

.github/CONTRIBUTING.md

@@ -15,7 +15,7 @@ please open an issue on GitHub.
 
 ## Experimental changes
 
-If your change can't be unit tested, we might ask that you add your change as an experiment so that we can verify your change works. To do this, first add a new option to [IGListExperiment](https://github.com/Instagram/IGListKit/blob/master/Source/IGListExperiments.h#L17).
+If your change can't be unit tested, we might ask that you add your change as an experiment so that we can verify your change works. To do this, first add a new option to [IGListExperiment](https://github.com/Instagram/IGListKit/blob/master/Source/Common/IGListExperiments.h#L17).
 
 Then, use an `experiments` bitmask wherever your change is and wrap it in a check to see if it is enabled: