use official sdk-go for cloudevent handling

[fsrv-xyz]

Hi there,

thank you for providing and maintaining that great software.

As I am using kubewatch with cloudevents, I investigated some unknown Message encoding errors in combination with the reference Golang SDK and detected the “by hand” implementation in this project.

In order to be and stay more compatible with that standard, an implementation using this SDK would be great.

Kind regards
Florian

[patrickdung]

@fsrv-xyz , if I am correct, the PR 53 is updating the CE log to binary format.

The current CE log format used by kubewatch seems having problem.
The content is in structured format but the HTTP content header is using application/json instead of 'application/cloudevents+json'