Change API.search() to use endpoint v1.1

Here's my proposed changes for switching to the API version 1.1 search endpoint.
Fairly simple changes with some breaking changes due to how the response
has changed from Twitter. Instead of returning a set of "SearchResult" the endpoint
now provides just plain "Status" objects.

When you call API.search() you get back an extended version of ResultSet
(which extends list) called SearchResults that has some meta data such
as "max_id" and "since_id" which is useful for pagination.

Here's a basic example: https://gist.github.com/joshthecoder/b9cd1c805a35da5fe43d

Would appreciate any feedback.