Added SiteSummary class and made site_listing() use it.
Added EngineSummary class and made engine_listing() use it.
Changed engine and site listing method names.

The engine and site listing method names now conform to the official Nexpose API naming convention.
Moved the request() method out of the Connection class.

This will allow for future restructuring to add in more classes for things
like 'Site' object classes and methods under those classes (especially the load() method).
This is part of bringing the code into line with the official Nexpose API conventions.
Fixed all the request() calls that broke when I moved that method :)
Added Site class.

If given two strings (name, scan_template), the Site class will create a new Site.
If given a Connection and integer, it will load the the Site with that integer id.

Saving a Site back to the console is not implemented yet.
Resolve conflicts
Merge pull request #2 from Red5d/master

Changes to align the code more closely to the Nexpose API standards and refine the way results for some methods are returned.