Tmux: create new panes and windows in current path

This was the behavior of older Tmux that was lost when I upgraded to
Tmux 1.9a. I missed this behavior, and thankfully I can preserve it by
binding my split and window keys to use the `-c` option [1].

[1]: http://unix.stackexchange.com/a/118381/83974
Vim: add Jasmine afterEach() snippet

I had a beforeEach() but not an afterEach() one. This commit adds it and
makes the description of my beforeEach() snippet more accurate.
Vim: add propTypes jsx snippet

I've been adding propTypes to my React components lately and wanted a
snippet to help speed up this work.