Add augroup: EqualWindowsOnResize

- Do `wincmd =` on `VimResized` event
Update plugins

- Add YouCompleteMe

- Update .gitmodules to include branch data
Modify 'tags'; search for `.git/tags`

- Also don't look for `TAGS`
Override default `do` and `dp` mappings; add `du`

- `do` and `dp` now accept counts (which refer to the buffer id). `du`
  is a shortcut for `:diffupdate`