Vim: Changes the way for searching things

- Remove NERDtree and NERDtree-tabs bundles. They were using to navigate
  on filesystem only. The way them do that is not so efficient.
- Replace NERDtree function with LustyFilesystemExplorer bundle. With it
  you can navigate on Filesystem using fuzzy search. Useful when you
  forgot the name of file but knows where is it.
- Maps find keys to:
    - <c-p> find files
    - <c-k> find methods on buffer tag
    - <c-f> find in filesystem