Implement Supermarket Extension

[chris-rock]

This PR implement the ability to find profiles on Chef Supermarket:

Display available profiles:

$ inspec supermarket profiles                                    
Available profiles:
-------------------
 * nathenharvey/tmp-compliance-profile

Display details about the profile:

inspec supermarket info nathenharvey/tmp-compliance-profile
name:   tmp-compliance-profile
owner:  nathenharvey
url:    https://github.com/nathenharvey/tmp_compliance_profile/

description:   An InSpec compliance profile for use with Chef Compliance Server.

Execute a profile:

$ inspec supermarket exec nathenharvey/tmp-compliance-profile
..

Finished in 0.01352 seconds (files took 4.37 seconds to load)
2 examples, 0 failures

Alternatively you could also use:

inspec exec supermarket://nathenharvey/tmp-compliance-profile
..

Finished in 0.03779 seconds (files took 5.16 seconds to load)
2 examples, 0 failures

[arlimus]

Incredibly clear super simple extension with great implications, love it!!
Cheers @chris-rock