Allow slugs to be optional.
Add documentation
Merge pull request #1 from martindale/master

Allow slugs to be optional
multiple source for slug can be added
- multiple source for slugs can be added
fixed formatting
Merge pull request #1 from az7arul/develop

fixed formatting
Merge pull request #2 from az7arul/master

Slug can be created from combining several properties
Release 1.2.0
wtf
Default to not allow overrides.