Remove condition for Active Record <3.0

Now we only support Active Record 3.1 or higher.
Remove old IRB hacks, prefer pry for debugging
Add failing spec for Issue #14

Thanks to John Shahid for pairing with me and helping to isolate this
issue.
Disable eager loading, fixes #14

Eager loading doesn't work because of the way pg_search_rank is added
into the SELECT for the query.