"RCTRefreshControl" naming conflict with RN0.18

[rreusser]

Since FB open sourced their own RCTRefreshControl interface, there was a naming conflict. I've fixed it here by renaming this component to RNRefreshControl.

https://github.com/rreusser/RCTRefreshControl/tree/rename

To use, add to package.json:

"react-native-refresh-control": "git@github.com:rreusser/RCTRefreshControl.git#rename",

and follow the instructions where RCTRefreshControl has been renamed to RNRefreshControl.

I might stop just short of a pull request and coming up with a truly canonical version since we're trying hard to stay on top of the latest RN releases precisely so that we don't have to struggle with backward-compatibility of all of the modules we're using.

This was the first place I checked for fixes though, so feel free to use if it's useful!