add python 2.6 to travis testing again, because weakrefs are gone now
add python 2.6 to travis testing again, because weakrefs are gone now

jonashaag/jedi,dwillmer/jedi,tjwei/jedi,dwillmer/jedi,jonashaag/jedi,tjwei/jedi,WoLpH/jedi,mfussenegger/jedi,flurischt/jedi,WoLpH/jedi,mfussenegger/jedi,flurischt/jedi