Ignore binstubs and specify rake as a development dependency
Change API to give you a Query object, which you can get the url from
or execute it. This is a breaking API change.

Before:

    api.listing(blah)

After:

    api.listing(blah).url
    # => http://www.play-asia.com/...
    api.listing(blah).exec
    # => PlayAsia::Response
Bump the version number because of the breaking changes, and update the readme.