Add ultisnips to neocomplcache completion

Add UltiSnips snippets to neocomplcache completion dialog.

This comes in separate file because neocomplcache automatically expands its path and collects scripts in `autoload/neocomplcache/sources` dir. Script is automatically called when neocomplcache invokes its completion and it doesnt affect main functionality of UltiSnips in any way. 

Also there's a function `g:UltiSnips_Complete()` which can be used for TextMate-like snippet completing with tab ( this references to  [this bug](https://bugs.launchpad.net/ultisnips/+bug/883341) on LaunchPad and [this](https://github.com/Shougo/neosnippet/blob/master/doc/neosnippet.txt#L347) functionality of neosnippet ) . Here's example how to do it:

Add this to `.vimrc`
```vim
let g:UltiSnipsExpandTrigger="<NL>"
inoremap <silent> <tab> <C-R>=g:UltiSnips_Complete()<cr>
snoremap <silent> <tab> <Esc>:call UltiSnips_ExpandSnippetOrJump()<cr>
xnoremap <tab> :call UltiSnips_SaveLastVisualSelection()<cr>gv
```
I spent a lot if time with mappings and currenly only way to map something to `tab` when using UltiSnips is to map UltiSnips trigger key to something else because it keeps overwriting mappings from `.vimrc`

I haven't tested this with SuperTab, so there may be glitches

There still things left to do: Documentation; Also I dont like current sutuation with mappings