Add support for media guide objects

[Jonathan-Zollinger]

support working with media guide objects

• Search Guide Media
• Create Guide Media
• Create Upload URL for a Guide Media object
• Show Guide Media object
• Replace Guide Media Object
• Rename Guide Media object
• Delete Guide Media object

This is complete when docs are supplemented with example usage (both successful calls and failures), and tests validate Zendesk's documented behavior - successful calls and failures (i.e. the updateUserSegment endpoint returns a 200 error code and the userSegmentObject created, thus tests should validate this and nothing more).