Prevent multiple consecutive dashes in slug.
Change the regex in spec/requests too
Test for multiple-dashes regression
Revert "Test for multiple-dashes regression"

This reverts commit 0065f7a5f9bb84d0ade9881f8199cc9a81f3a303.
Unit test of the slug pattern
Merge pull request #65 from invotra/slug-regex

Slug regex