Revert "Move to lightline"

This reverts commit e4a8fedb40.

vimrc

@@ -29,17 +29,16 @@ else
   set title
 endif
 
-" Lightline
-let g:lightline = {
-      \ 'colorscheme': 'nord',
-      \ 'active': {
-      \   'left': [ [ 'mode', 'paste' ],
-      \             [ 'gitbranch', 'readonly', 'filename', 'modified' ] ]
-      \ },
-      \ 'component_function': {
-      \   'gitbranch': 'FugitiveHead'
-      \ },
-      \ }
+" Airline
+let g:airline_theme='raven'
+if !exists('g:airline_symbols')
+  let g:airline_symbols = {}
+endif
+let g:airline_left_sep=''
+let g:airline_right_sep=''
+let g:airline_symbols.linenr = ''
+let g:airline_symbols.branch = '⎇'
+let g:airline_symbols.whitespace = ''
 
 " Terminal behavior and appearance
 if !has('gui_running')