Summary:
- Fix a few things related to how npm should publish the package (sources were in the gitignore file, so I think it would have break the build during install - I fixed this by adding a npmignore that should override the gitignore rules)
- The enumerations values are now generated directly from `enums.py`
- I added percent unit support (#258) to the bindings (`.setWidthPercent` is currently exposed, but I've also added a very very little parsing to also support `.setWidth("100%")` and `.setWidth(.getWidth())`), added the missing tests, and fixed Travis.
Closes https://github.com/facebook/yoga/pull/314
Reviewed By: mikearmstrong001
Differential Revision: D4377198
Pulled By: emilsjolander
fbshipit-source-id: 774dfafd416f5421f3be59a1d181eb7056487abe
