With blocks now being immutable, use big.Int values from
accessor functions instead of copying their results.

This pleases the RPC tests.

TestMadeupParentBlockChainAttack has been deleted because it was too
hard to port and the attack that it checks the prevention of is being
averted in a different way (through a protocol change).

Debug develop

p2p: support protocol version negotiation

Travis and README cleanup

Monitor fixes

Metrics collecting and reporting support

IPC interface improvements