discourse/discourse — pull request #164 by danneu (2013-02-14 23:06:27+00:00)
Title: slug should replace underscores

`String#parameterize` already hyphenates, but it doesn't convert underscores since they're url-valid.

# Before
Slug.for("o-o_o-o") #=> "o-o_o-o"

# After
Slug.for("o-o_o-o") #=> "o-o-o-o"