change the regex engine according to warning (#449)

* change the regex engine according to warning
the readme won't tell the user to change the regexpengine now that the correct one is set

Author: bounceme

README.md

@@ -102,18 +102,6 @@ proposed change and how it is valuable.
 Report a bug on [GitHub Issues](https://github.com/pangloss/vim-javascript/issues).
 
 
-## A Quick Note on Regexes
-
-Vim 7.4 with patches LESS than 1-7 exhibits a bug that broke how we handle
-javascript regexes. Please update to a newer version or run the following
-commands to fix:
-
-```
-:set regexpengine=1
-:syntax enable
-```
-
-
 ## License
 
 Distributed under the same terms as Vim itself. See `:help license`.

ftplugin/javascript.vim

@@ -1 +1,4 @@
 setlocal suffixesadd+=.js
+if (v:version < 704 || (v:version == 704 && !has('patch002'))) && exists('&regexpengine')
+  set re=1
+end