Is EqualTo to allow “containsAll” mode for array and object

[ashleyfrieze]

Partially fixed by #29

[ashleyfrieze]

Contains, rather than equals is available on array, but not object.

E.g.

{ "a": "someA", "b": "someB"}

// does contain

{ "a": "someA" }

maybe:

assertJson(actual)
   .where().at("/").objectContains()
   .isEqualTo(expected);