RIP Shougo plugins. Remove vimshell and vimproc

- I'm finally removing the last of the Shougo plugins vimshell.  I'm
  going to be switching from gvim to tmux so this plugin won't be
  necessary anymore
- The reason for the switch is that I don't actually use any of the
  benefits that the GUI provides (don't use the menu, or the mouse, no
  <M-> mappings, etc.) and I'm missing the benefits that tmux provides
  (integrated environment, sane shell access, repls that don't suck,
  etc.)
Configure Tmux.  Add Dispatch and Tbone plugins.

- Replace mappings that no longer work in tmux because their output is
  captured by the terminal emulator
- Add mappings for navigating tmux panes between vim and tmux
- Add StartRepl function to open a repl in a vsplit using Dispatch
Reduce increment in window resize mappings. Less columns to work with in tmux