json-path-assert for json related unit tests

[Kirk Lund]

To support fixing up unit tests that involve json, I'd like to add in a
dependency on com.jayway.jsonpath:json-path-assert.

We already have a dependency on com.jayway.jsonpath:json-path (for
spring-hateoas). json-path-assert basically adds some new Hamcrest matchers
for clean assertions involving json.

I intend to use this in TypedJsonJUnitTest (GEODE-1842) because that
test doesn't currently have assertions(!).

-Kirk