Added new slug extensions

Update to allow {category} and {author} in urlFormat. Can also specify
slug as {slug}
Added new slug extensions

Update to allow {category} and {author} in urlFormat. Can also specify
slug as {slug}
Merge branch 'master' of https://github.com/MacsDickinson/Sandra.Snow

Conflicts:
	src/Snow/Extensions/SlugExtensions.cs
updated barbato dlls to contain snow update
Merge pull request #72 from MacsDickinson/master

Added new slug extensions