Update ZendeskApi.cs
Update ZendeskApi.cs

Added proxy support for the core. This will help to debug request/response using fiddler or similar tool.

Note: This change request is related to My previous change request to Core.cs.
dcrowe/ZendeskApi_v2,mwarger/ZendeskApi_v2,CKCobra/ZendeskApi_v2,mattnis/ZendeskApi_v2