Remove built-in versioning support.

The trade off between code complexity and benefits just wasn't worth it.
Also the approach was forcing generators to implement one way of doing
versioning removing the freedom from end users to implement it the way
they needed.
There is now one design per version. All generators operate in the
context of a single version.

Author: raphael

context.go

@@ -46,8 +46,6 @@ type (
 		Payload interface{}
 		// Params is the path and querystring request parameters.
 		Params url.Values
-		// Version is the name of the targeted version if any, empty string otherwise.
-		Version string
 	}
 
 	// ResponseData provides access to the underlying HTTP response.