Added setting to theme, added placeholder attribute to search box. It is
not working though. It is passed in properly to the render() function,
but the placeholder attribute is not actually added to the search box.
In testing I found that it worked just fine when I added it to one of
the hidden fields in the same form.
Implemented using javascript instead. It actually works
Merge pull request #17 from bricej13/search

Added custom search box placeholder functionality