replace rejects an object member named "-", so make_patch can produce patches that fail to apply #212

replace raises InvalidJsonPatch for every path whose last token is -, including when - names an object member rather than the end of an array. make_patch emits replace for a changed member, so it can produce patches that apply then rejects:

>>> import jsonpatch
>>> patch = jsonpatch.make_patch({'-': 0}, {'-': 1})
>>> patch.patch
[{'op': 'replace', 'path': '/-', 'value': 1}]
>>> patch.apply({'-': 0})
jsonpatch.InvalidJsonPatch: 'path' with '-' can't be applied to 'replace' operation

test and remove handle the same path correctly; remove of /- turns {'-': 0} into {}. RFC 6901 gives - a special meaning only when the referenced value is an array. For an object it is an ordinary member name. Rejecting /- in replace on an array is correct, because it refers to a nonexistent element.

Cause: ReplaceOperation.apply checks part == "-" before looking at the type of subobj.

Suggested fix: only reject - when subobj is a sequence.

Tests: these tests in property_tests.py are marked @unittest.expectedFailure because of this bug; drop the markers once it is fixed:

• OperationProperties.test_replace_any_existing_location
• MakePatchProperties.test_roundtrip

On current master (e0e7703) this is the only failure Hypothesis finds for test_roundtrip. With - keys excluded, the roundtrip passed 80,000 generated document pairs across 4 hash seeds.