Make sure that we're fetching the hash from the current chain and not
the canonical chain.

Conflicts:
	core/vm/environment.go

core/state: deleted field in StateObject Copy() and unit test
(cherry picked from commit 90f1fe0e)

currently, under normal circumstances, you always set the timestamp to previous.Time() + 1.
credits to https://www.reddit.com/r/ethereum/comments/3jcs5r/code_avg_block_time_vs_difficulty_adjustment/cuoi4op

style

core: improve block gas tracking
(cherry picked from commit e9b031b8)

Add tests for uncle timestamps and refactor timestamp type
(cherry picked from commit abce0995)

user agent messages were dumped in some cases
(cherry picked from commit a219159e)

fdtrack: hide message

rpc/comms: reconnect ipc client after write error

p2p, p2p/discover: small fixes 

This reverts commit 5c949d3b.

eth: fix an issue with pulling and inserting blocks twice

PR #1621 changed Table locking so the mutex is not held while a
contested node is being pinged. If multiple nodes ping the local node
during this time window, multiple ping packets will be sent to the
contested node. The changes in this commit prevent multiple packets by
tracking whether the node is being replaced.

Might solve #1579

cmd/geth: Fix chain purging from cmd line

crypto: remove obsolete code

Switch from Coveralls to Codecov code coverage service

Updated README, Added CONTRIBUTING

core, miner: write miner receipts

rpc/api: return boolean value for eth_submitHashrate

rpc: update the xeth over RPC API to use the success/failure messages

GPO update