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.