Fixed coding style issues
Add addRule example
Merge branch 'master' of github.com:mac2000/slugify into mac2000-master

* 'master' of github.com:mac2000/slugify:
  Add addRule example
  change in Czech slug of D/d with caron
  change in Czech slug of D/d with caron
Improved description of addRule() in README
Merge branch 'mac2000-master'

* mac2000-master:
  Improved description of addRule() in README
  Add addRule example
  change in Czech slug of D/d with caron
  change in Czech slug of D/d with caron