Adding coinrpc to pybitcoin

This merge has the following properties:

1) Rewrote the history of coinrpc so that all revisions are local to dir rpc/
2) 'git log coinkit' will give the revision history of folder coinkit and so on
3) Individual file commit/contribution history should remain intact for all files
4) The 'rpc' branch makes no changes outside of rpc/ folder, so shouldn't break anything

The method of merging was inspired by http://stackoverflow.com/a/21495718/1827801 and is different from using a git subtree