Add a CLI

[Julian]

It's been requested enough, we might as well include some form of CLI for doing basic (or not so basic?) validation tasks.

[sigmavirus24]

Why not make it a separate package which simply requires jsonschema? Were I to use jsonschema for a different library, I wouldn't want to be forcing my users to install a CLI along side a library.

[Julian]

What disadvantage or extra work does this cause your users?

[sigmavirus24]

It pollutes their system with command-line utilities they did not want in the first place.

[Julian]

That's kind of reasonable. I don't consider a single unobtrusively named binary to be likely to cause any issues for anyone, and this is really more of a Python-packaging-ecosystem concern than anything specific. But sure, I'd consider making this optional.