Use go modules instead of dep

[itayd]

Not sure if you have a policy around this, but moving to go modules is fairly simple, all that needs to be done is:

$ go mod init github.com/uber-common/cadence-samples

and remove the dep stage from the Makefile.

The motivation, at least for me is to avoid having to put stuff in a GOPATH.

btw, if this is ok with you, will be happy to do it.

[ernado]

Seems like it was resolved in #26 :)

[itayd]

Ha, same day.