gateone.py:  Gate One will now use a mostly-persistent file cache for minifying files that lasts between restarts of gateone.py.  By default it will use tempfile.gettempdir()/gateone_cache but this can be overridden with the 'cache_dir' 'gateone' setting.  If anyone thinks it is necessary I can also add a command line argument for it.
gateone.py:  Fixed a bug that would result in an IndexError exception if a client failed the origin check.  Tracked in #182 (https://github.com/liftoff/GateOne/issues/182).
gateone.py:  The 'cache_dir' setting now gets set automatically if unavailable inside of ApplicationWebSocket.open().  Previously this logic was duplicated every time something needed to figure out the cache_dir.  So the benefit here is that applications/plugins don't have to worry about that value being unset anymore.
utils.py:  Rewrote short_hash() because it had a tendancy to create collissions when given long strings that started out with the same characters.
Bookmarks, SSH, and Logging plugins:  Updated their send_css_template() functions so that they use the persistent file minification/cache more appropriately.  Before this they would end up leaving leftover files with each restart of gateone.py.