Let folds open if &foldopen contains 'search'

Since vim-sneak does not work with the /-command but with the searchpos-function, the opening of folds must be done explicitly.
The skipping of the content of closed folds if &foldopen does not contain 'search' should also be implemented in the future. See justinmk#102.

plugin/sneak.vim

@@ -172,6 +172,11 @@ func! sneak#to(op, input, inputlen, count, repeatmotion, reverse, inclusive, str
   endif
   "search succeeded
 
+  " if &foldopen contains search, folds are opened when jumping to matches
+  if !empty(matchstr(&foldopen,"search"))
+      norm! zv
+  endif
+
   call sneak#hl#removehl()
 
   if (!is_op || a:op ==# 'y') "position _after_ search