change startup check regex once again

I'm terribly sorry for excluding all MacVim users.

Closes #14.

plugin/startify.vim

@@ -15,7 +15,7 @@ let g:startify_session_dir = resolve(expand(get(g:, 'startify_session_dir',
 augroup startify
   autocmd!
   autocmd VimEnter *
-        \ if !argc() && (line2byte('$') == -1) && (v:progname =~# '^g\=vim') |
+        \ if !argc() && (line2byte('$') == -1) && (v:progname !~# 'g\=vimdiff\|view\|evim') |
         \   call s:insane_in_the_membrane() |
         \ endif
 augroup END