Issue #33: Add jq to Dockerfile

[philippeboyd]

Seems like issue #33 hasn't been fix properly. I agree that jq should be part of the docker image. It's really helpful to parse json formatted secrets.

[hashicorp-cla]

All committers have signed the CLA.

[philippeboyd]

Looking at commit 02af941, why was jq removed ?

[jefferai]

I believe the version of jq available in the repos at the time had known security issues.

[jefferai]

Either that or Alpine 3.6, which it moved to at the same time, didn't have jq -- likely because of the outstanding security issues.