Use a single key for switching between emacs splits

I don't use splits often, and when I do, it's only 2. A single cyclic
key should meet my needs.
M-- and M-+ to change font sizes
A font size of 160 is good for a laptop
Helpful snippet-editing trick from Harry
Projectile ack and dired
Fix some evil usability settings
Show both TODOs and DONE items in org mode
Shortcut to insert setext header lines in markdown
Comment cleanup
Make M-number keys switch tabs
Fill column indicator plugin
Fill column indicator isn't ready for prime time yet
Preliminary spellchecking setup
Powerline
Treat ruby file types as ruby
Initial clojure config