allow open_environment to cache results.
pep8 improvements (should be no semantic difference)
Cleaning up project install and framework.

 * Single file project, don't need extra package dir
 * Remove lots of unneeded cruft from setup.py
 * Add a README.md
 * Fix dependency_link for TracSQLHelper to make it more easily installable.
 * bump version to 0.3
Perform an explicit cast of ticket_id to a string; prevent sql injection

This improvement was suggested by rjollos
https://github.com/UnwashedMeme/TicketMoverPlugin/commit/f22d08ae1cf71c0545eb664a96b36c10adc35658#commitcomment-3271651
Use self.log instead of self.env.log
Better logic for moving to a trac whose `base_url` isn't set

This is based on rjollos work in http://trac-hacks.org/changeset/13219