add shortcut for request context

[kedric]

Add shorthand context at request level by duplicate two methods:

• Receive(successV, failureV interface{}) -> ReceiveContext(ctx context.Context, successV, failureV interface{})
• ReceiveSuccess(successV interface{}) (*http.Response, error) -> ReceiveSuccessContext(ctx context.Context, successV interface{})

They have same principe but call req.WithContext(ctx) before Do(req, successV, failureV)

[kedric]

Duplicate from #73