Merge branch 'feature/p2p-protocol-interface' of https://github.com/fjl/go-ethereum into fjl-feature/p2p-protocol-interface

Submit code coverage to coveralls only on travis build success

* Renamed a couple more chain => core
* Updated VM `pc` to be uint64 rather than big int
* XEth interface cleanup

This moves call and create to the specified environments. Vms are no
longer re-used. Vm uses environment's Call(Code) and Create in order to
execute new contracts or transfer value between accounts.

State transition now uses the same mechanism described above.