Foursquare input and query nodes

This should replace pull request #15 as it contains both the query and input nodes for Foursquare. The input node polls every 15mins for new check ins by the registered user. The query node enables the user to trigger a request to gather information about the check-ins by the registered user. The input node only returns if the information has changed, the query node always returns what it finds. 

Somehow I seem to have a change to the project version number included in this request - I haven't had a chance to figure out why this occurred (occurred whilst I was squashing commits) but I wanted to get this pull request in before I left.

Any comments welcome.
In fact, we should check the credentials look valid when the node is created. If they don't look right, warn the user and return then - no need to wait until messages start flowing to warn about it repeatedly.