Test-tastic.

RLP: remove signed integer support and other fixes

Decode error messages now say "expected input list for foo.MyStruct"
instead of just "expected List".

The documentation for reflect.Value.Index states that it will
panic for out-of-bounds indices. Since go 1.4, it actually panics.

There is no agreement on how to encode negative integers
across implementations. cpp-ethereum doesn't support them either.

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.