Add vimux; update vimrc

With this commit we now have the ability to run specs from vim while in
a tmux session by hitting <leader>r or <leader>R. With this vimrc we
have a 80/20 horizontal split to the tmux pane we're working in.

.gitmodules

@@ -79,3 +79,6 @@
 [submodule "bundle/vim-vroom"]
 	path = bundle/vim-vroom
 	url = git://github.com/skalnik/vim-vroom.git
+[submodule "bundle/vimux"]
+	path = bundle/vimux
+	url = git@github.com:benmills/vimux.git

vimrc

@@ -144,7 +144,7 @@ nnoremap <c-l> <c-w>l
 " paste mode / paste from system / kill paste mode
 map <leader>p :set paste<CR>o<esc>"*]p:set nopaste<cr>
 
-" format file
+" clean up file formatting
 map <leader>i mmgg=G`m<CR>
 
 " NERDTree mapping
@@ -158,3 +158,9 @@ imap <c-l> <space>=><space>
 
 " Show/hide line numbers
 map <leader>n :set nonumber!<CR>
+
+" Run vroom in vimux
+let g:vroom_use_vimux = 1
+
+" Configure vimux to run a horizontal split
+let g:VimuxOrientation = 'h'