Don't shut down fifo/thread after each commit

This incorporates taskthread into pyvertica, so the query command can be rerun on the same therad, without deleting the fifo.

Let me know what you think, this is higher risk than other changes I've propsed, but I've also done some testing and it seems to work.

Boyscout rule, there were a lot of pep8 errors on my machine that didn't get caught by travis, so I've fixed them up in this branch, too.