Fixed newsub()

Removed reference to 'amount' which shouldn't be there.
Fix newoffer()

newoffer() method didn't set the 'currency' property which was required.
Update docs on newoffer()
No amount in subscriptions
send the client as well when creating a new card
Fixed newcard() which was ignoring client id. Added updatesub()
Merge commit '7cc44564f923d37a3623333240801b1c661913f9'

Conflicts:
	pymill/pymill.py
Merge remote-tracking branch 'sebslomski/master'

Conflicts:
	pymill/pymill.py