Remove empty quotes when category is empty.

When category = ""

Should print "category: " to file, current behaviour prints "category:
\"\"".

Latter creates an actual category, with a blank title. All posts created
since this update, without a category explicitly written in `rake`
command, or post directly edited, will belong to this category.
Simpler logic to category patch

Replace single line with cleaner, more readable Ruby.
Merge pull request #198 from parnmatt/patch-1

Remove empty quotes when category is empty.
new
delter Merge branch 'master' of github.com:happyroc/happyroc.github.com

Conflicts:
	Rakefile
	_config.yml
	_includes/themes/twitter/default.html
	_layouts/default.html
	_layouts/page.html
	_layouts/post.html
add