Add some plugins I'm developing to vimrc
Finally fix all the clipboard issues

- Set the tmux default command to use 'reattach-to-user-namespace' so that
  programs started in tmux have access to the system clipboard (MacVim being the
  first example)
- Set the vim clipboard to the 'unnamed' register ("*), so that all the
  anonymous yank and deletes go to the system clipboard too
Refine some NERDTree configuration options
Clean up the git post-commit hook