No Intro for Categories

No need for the post intro on category pages.
"category" instead of "categories"

Thinking "category" instead of "categories" makes more sense for single
category URL's.
Lowercase Category URL's
Fixes #163
pagination links should be from same url path, not from root
Merge pull request #167 from bndr/infinite_pagination

fix for #165
Link Back to Home on Category Pages
Merge branch 'master' of github.com:circa75/dropplets

Conflicts:
	templates/simple/post.php
	templates/simple/posts.php