Use C-j to activate tmux instead of C-a

Now, I can use C-a in Readline again, yay!
Use C-a to go to last window
Use the shorthand when setting options
Start pane numbering at 1
Highlight the window when it has new activity
Re-number windows when one is closed
New shorthand for creating a lower 25% split
Remove unused stuff
Use editorconfig for vim
Use HAML syntax highlighting for vim