migrate to github actions and update deps

[shamil]

This PR migrates to github actions and removes travis. A test run passes se results in my fork.
@Theaxiom I guess you need to enable actions, as described here.

[Theaxiom]

Is consul-cli still a useful tool? I wasn't aware anyone was still using it.

[shamil]

I'm using it ;) consul built-in cli doesn't support all the consul API features, so consul-cli is usefull for me.
If this project considered unmaintained, I could maybe take it and try continue maintaining, it's up to you.

[shamil]

@Theaxiom what do you think? Is it acceptable to let me maintain this project going forward?