Upgrade Gitlab, Github, Guzzle libraries

[jelovac]

Any thoughts on upgrading the Guzzle library to a newer version?

While installing the package I got the notification that: Package guzzle/guzzle is abandoned, you should avoid using it. Use guzzlehttp/guzzle instead.

This can introduce some potential security risks since the old guzzle package is no longer maintained.

[tyler-sommer]

This dependency is introduced by the Gitlab and Github integration libraries we use. We need to update both integrations to get this done.

See #63 for the Gitlab upgrade. We need to do a similar thing for the Github library.

[tyler-sommer]

#63 has been merged. Still need to take a look at the github-api dependency, though it looks like we can simply remove the guzzle/guzzle dep.