Revert "Add possibility to disable identifier completion engine"

This reverts commit 44d5747d23.

Conflicts:
	README.md

README.md

@@ -656,10 +656,8 @@ option is set to `2`, then when the user types a second alphanumeric character
 after a whitespace character, completion suggestions will be triggered. This
 option is NOT used for semantic completion.
 
-Setting this to `-1` will disable the identifier completion engine; only the
-semantic engine will remain. NOTE: this also turns off other engines that tie
-into the identifier completion engine, like UltiSnips trigger completion or
-filename completion.
+Setting this option to a high number like `99` effectively turns off the
+identifier completion engine and just leaves the semantic engine.
 
 Default: `2`
 

autoload/youcompleteme.vim

@@ -520,10 +520,6 @@ function! s:InvokeCompletion()
     return
   endif
 
-  if g:ycm_min_num_of_chars_for_completion < 0
-    return
-  endif
-
   if s:InsideCommentOrStringAndShouldStop() || s:OnBlankLine()
     return
   endif