Replace 'INLINE' tags with 'EXPR' tags in form_for snippets.

In eruby 'form_for' snippets, I changed the ERB tag-style from '<% %>' to '<%= %>' to be compatible with Rails 3 and newer.

As of Rails 3, form_for uses '<%= %>' tags rather than '<% %>'.
Omitting the equal sign will work in Rails 3 (though with a deprecation warning) but not Rails 4.