Add dir-creation to setup, fix tmux/weather.py.

res/setup.json, setup.py
	-Add dir creation to the setup script, to support my tmux
	config's use of a custom `~/.tmux_cache`.

tmux/(email -> gmail).py
	-The name `email` conflicted with a standard Python module,
	so rename to `gmail`.

tmux/weather.py
	-Fix the `OSError` thrown when the file named `CACHE_FILE` did
	not exist (as will be the case on new machines) by inserting a
	conditional.