Abort timed out connections with abortConnection()

Timed out connections are not always killed with transport.loseConnection().
Call transport.abortConnection() instead.

http://twistedmatrix.com/documents/12.2.0/core/howto/servers.html

This fixes the memory leaking issues.
Merge pull request #81 from varatada/master

Abort timed out connections with abortConnection()