[developers] Adding new sites to the whitelist

To add a new site to the whitelist, do the following:

1. Add a new file to src/main/resources/whitelists
2. Reference that file from Whitelist.WHITELISTS as described in the comment in https://github.com/getlantern/lantern/blob/master/src/main/java/org/lantern/Whitelist.java