Update RawGit URLs.

1) Use the updated name, RawGit, instead of RawGithub.

2) Use the CDN, which is made for production use cases and does not have a throttle limit. Otherwise, users will end up seeing a blacklisted screen, as can be seen here: 

http://rawgit.com/noelboss/featherlight/master/release/featherlight.min.js