Adding Explicit Refine & Paging Functions

Including public methods for controlling the state of the helper before
starting a search. This has been very useful when creating "facet UI's"
which have hierarchical data structures, adding fully featured paging
controls and dealing with infinity scroll.
Merge pull request #13 from james-andrewsmith/fine-grain-refinement-and-paging

Adding Explicit Refine & Paging Functions (1/2)