use fzf instead of ctrl-p

Brewfile

@@ -1,2 +1,4 @@
 tap 'thoughtbot/formulae'
 brew 'rcm'
+brew 'fzf'
+brew 'the_silver_searcher'

vimrc

@@ -49,23 +49,6 @@ if count(g:vimified_packages, 'general')
   Plugin 'tpope/vim-unimpaired'
   Plugin 'tpope/vim-vinegar'
 
-  Plugin 'rking/ag.vim'
-  function! AgGrep()
-    let command = 'ag -i '.expand('<cword>')
-    cexpr system(command)
-    cw
-  endfunction
-
-  function! AgVisual()
-    normal gv"xy
-    let command = 'ag -i '.@x
-    cexpr system(command)
-    cw
-  endfunction
-
-  map <leader>a :call AgGrep()<CR>
-  vmap <leader>a :call AgVisual()<CR>
-
   Plugin 'tpope/vim-surround'
   " Add $ as a jQuery surround, _ for Underscore.js
   autocmd FileType javascript let b:surround_36 = "$(\r)"
@@ -84,25 +67,32 @@ if count(g:vimified_packages, 'general')
   map \ :NERDTreeToggle<CR>
   map \| :NERDTreeFind<CR>
 
-  Plugin 'ctrlpvim/ctrlp.vim'
-  let g:ctrlp_match_window = 'bottom,order:ttb,min:1,max:10,results:10'
-  let g:ctrlp_clear_cache_on_exit = 0
-  let g:ctrlp_max_files = 0
+  Plugin 'junegunn/fzf'
+  let $FZF_DEFAULT_COMMAND= 'ag -g ""'
+  nnoremap <C-p> :FZF<CR>
+  nnoremap <silent> <leader>f :FZF<CR>
 
-  nnoremap <silent> <leader>f :CtrlP<CR>
-  noremap <leader>b :CtrlPBuffer<CR>
 
-  Plugin 'FelikZ/ctrlp-py-matcher'
-  let g:ctrlp_match_func = { 'match': 'pymatcher#PyMatch' }
+  Plugin 'junegunn/fzf.vim'
+  let g:fzf_layout = {'down': '40%'}
+  let g:fzf_tags_command = 'ripper-tags -R'
+  noremap <leader>b :Buffers<CR>
 
-  if executable('ag')
-    " Use Ag over Grep
-    set grepprg=ag\ --nogroup\ --nocolor
+  map <leader>a :call fzf#vim#ag(expand('<cword>'), fzf#vim#layout())<CR>
 
-    let g:ctrlp_user_command = 'ag %s -i --nocolor --nogroup --ignore ".git" --ignore ".DS_Store" --hidden -g ""'
-  else
-    nnoremap <silent> <leader>F :ClearCtrlPCache<CR>\|:CtrlP<CR>
-  endif
+  function! s:get_visual_selection()
+    " Why is this not a built-in Vim script function?!
+    let [lnum1, col1] = getpos("'<")[1:2]
+    let [lnum2, col2] = getpos("'>")[1:2]
+    let lines = getline(lnum1, lnum2)
+    let lines[-1] = lines[-1][: col2 - (&selection == 'inclusive' ? 1 : 2)]
+    let lines[0] = lines[0][col1 - 1:]
+    return join(lines, "\n")
+  endfunction
+
+  command -range AgVisual call fzf#vim#ag(s:get_visual_selection(), fzf#vim#layout())
+
+  vmap <leader>a :AgVisual<CR>
 
   " File Renaming (credit: garybernhardt)
   function! RenameFile()