Need tests for: Framing matches on specified value

I noticed a discrepancy between JSON-LD Playground and RDF Distiller.

If there is a property with a value defined in the frame, then the frame
matching algorithm should match on that value.

jsonld.js does not support this feature currently, but RDF Distiller does.
See: https://github.com/digitalbazaar/jsonld.js/issues/300

I wrote a fix and I think the tests I wrote will be helpful for alignment
between engines.

I opened a GitHub issue here:

https://github.com/w3c/json-ld-framing/issues/99

and I have a pending PR with 3 potential tests here:

https://github.com/w3c/json-ld-framing/pull/100

Thanks!
Michael Puckett