Removed vim-nerdtree-tabs to fix Name Collision

vim-nerdtree-tabs was being installed twice and since Vundle prevents users of having 2 plugins with the same name on the .vimrc file.

It's duplicated here https://github.com/timthrillist/minimum-awesome/blob/master/vimrc.bundles

```
Vundle error: Name collision for Plugin jistr/vim-nerdtree-tabs. Plugin jistr/vim-nerdtree-tabs previously used the name "vim-nerdtree-tabs". Skipping Plugin jistr/vim-nerdtree-tabs.
```

Related:
https://github.com/gmarik/Vundle.vim/issues/494