Add RPC & client call to replay a transaction.

[gavofyork]

No description provided.

[coveralls]

Coverage decreased (-0.06%) to 86.968% when pulling 399a274 on replay-transaction into a9ae6e3 on master.

[tomusdrw]

How about this:

let address = try!(self.transaction_address(id).ok_or(ReplayError::TransactionNotFound));
let block_data = try!(self.block(BlockID::Hash(address.block_hash)).ok_or(ReplayError::StatePruned));
let mut state = try!(self.state_at_beginning(BlockID::Hash(address.block_hash).ok_or(ReplayError::StatePruned));

let block = ...

if address.index >= txs.len() {
  return Err(ReplayError::TransactionNotFound);
}
...

to avoid nesting?

[coveralls]

Coverage decreased (-0.3%) to 86.767% when pulling 7128dac on replay-transaction into a9ae6e3 on master.