nil attr-value will cause removeAttribute to be called.
Make sure more than two chained classes are translated.

The interop .replace will only replace the first instance of
needle. Using clojure.string/replace will swap out all instances of
needle and thus allow more than two chained classes.
Merge pull request #26 from philjackson/master

Make sure more than two chained classes are translated.
Use a RegExp directly as in clojure.string for replacing periods with spaces.
Merge branch 'master' into develop