Normalizes the URLs before saving in database.
Fixes treatment of fatal connection errors.
requirements.txt: Loosen restriction on lxml.
Groups the options.
Implements --no-clobber, --timestamping.
http.py: Catches only socket related exceptions.
Adds http short close test.
writer.py: Removes utime keyword parameter.
Fixes recorders not working.
Implements --continue.
util.py sleep(), wait_future(): Uses current ioloop instead.
Sets the unittest connection timeout values.
Gets the result from future directly within wait_future().

Avoids losing exceptions.
Increases unit test connection read timeout.
Merge branch 'develop'
Bumps version to 0.4.