Remove stan-snippets package
Disable flymake in stan-mode
Add R shebang snippet
Switch yas trigger key and use globally

At some point, I was having issues with yas and Org mode conflicts, so I
only enabled yas in LaTeX and programming mode buffers. I'm enabling it
globally again and moving the expand trigger to a key chord.
Make org-open-file available in dired
Restore misc capture templates

These were deleted in d2ed8d9 (along with the backburner templates), but
it's useful to have these for non-TODO items because, unlike the
backburner items, these don't fit well with refiling from tasks.org.
Change method for defining gnus bindings
Move some hook bindings to mode maps
Define prefix key for global Org keys