fix vimrc of version dectect and calling procedure for neocomplete

* since neocomplete can work on Vim 7.3.885 and up, for 7.4 and later no patch is needed.
* NeoCompleteEnable should be called after neocomplete is sourced, use on_post_source() hook
Merge pull request #1 from ccwang002/patch-1

fix vimrc of version dectect and calling procedure for neocomplete