Don't include extra slash when autocompleting
Handle autocompleting for associated objects on new page

Previously this was broken as new isn't an allowed autocomplete
type.  Since we know when an association is being used, just
set it to association.
Fix searching by associated object that uses autocompletion

Those objects override the name parameter in column_options, so
merge the search name into that so that it takes priority.
Bump version to 0.5.3