vimrc: additions and fixes

* Fix line number display toggle.

* Add shortcuts for searching for the visually selected text.

* Pathogen, PEP8, JSHint, NERDTree bindings.

* Set leader to comma.

* Add quickfix window toggle.

* Set temporary file to ~/tmp/scratchbook.

* Capitalize <cr>.

Signed-off-by: Adrian-Tudor Panescu <adrian@panescu.com>
jshint: new version

Signed-off-by: Adrian-Tudor Panescu <adrian@panescu.com>