Improves the handling of port 0

Usually port 0 means that the OS should pick any free port. After
listen() has been called the picked port can be determined and used
from then on.
Fixes double space typo
Removes unnecessary NSAssert
Merge pull request #1 from ChristianKienle/master

Better handling of port 0
Fixed headers not being parsed properly when not received all at once
Small fixes
Removed dependency on CFSocket to be 100% GCD based
Merge commit 'a557080a07c70499b4d1a539345229b878934b3f'