Use browserify to build distribution

This is the final pull request to make PeerJS support browserify. The other two PRs browserify js-binarypack and reliable. Make sure to update package.json to point to the appropriate packages. The distribution is built using grunt instead of the homegrown build script.
Personal preference. It think its a bad idea to put precompiled assets into
a repo. If people use the github as primary means to obtain peerjs that
will have to be reversed ofc. The npm package does have the precompiled
versions for what its worth.