Update vim-json to the recommended version

The original vim-json has been [superseded](http://www.vim.org/scripts/script.php?script_id=1945) by [elzr's much-improved version](https://github.com/elzr/vim-json).  Pardon if you've already examined that version and decided against it, but if you haven't it's a must-see.
Merge pull request #16 from binaryphile/patch-1

Update vim-json to the recommended version
chore: add port key.json for navigating files
feat(plug): switch to git-nerdtree
feat(plug): add vim-unimpaired
docs: update star counts for readme plugins
feat(snippets): more ember snippets
Merge remote-tracking branch 'upstream/master'

Conflicts:
	README.md