Provide a generic way to do venue/explore request

[yaowentu]

I am using this Java client to send foursquare request. there is a venuesExplore method to call explore api, but it only takes some of the parameters not all of them. For exmaple "sortByDistance", "time", "day" etc are not configurable.

Can we add another generic venuesExplore method to take a map of parameter names and values like what we are doing for venuesSearch?

[yaowentu]

Fixed here: https://github.com/yaowentu/foursquare-api-java/commit/4bd539a1ddb9a6d937326a1d504f44f59e0c7e0c

By they way the junit test seems to be broken.