fix unconfirmed_transactions()
Merge pull request #528 from ouziel-slama/master

fix unconfirmed_transactions()
Merge pull request #530 from ouziel-slama/develop

fix
Merge branch 'master' into develop

Conflicts:
	lib/util.py
Process Locking on OS X

On Windows *and OS X*, use `socket.AF_INET` instead of `socket.AF_UNIT`.

Closes #529.
hex string in blocks.previous_block_hash