Add request class for extensions
Add extensions_for method
Add ProductServices object for YaST
Merge pull request #1 from wstephenson/review_140314_add_products_api_call

[Review] Request from 'wstephenson' @ 'wstephenson/rubygem-scc_api/review_140314_add_products_api_call'
Merge pull request #27 from wstephenson/master

Products implementation