Added content for payloads skeletons.
Added payload type with GetPayloadBytes-method.
Errors are now returned.
Multipart form encoding should be sorted now.
"SimpleHTTPRequest" has been renamed to HTTPRequest.
Changed return types of everything and moved stuff around. Added parsing to single structure or "one of" (see parsing.go) from JSON or XML.
Added content type with boundary support.
Added some helper methods.
Changed payloads to be more key-value based. Multiple values can now be assigned to the same key - this will be encoded properly when sending the requests.