modified 'patch' tests in order to use parsed json objects instead of strings

while running the test (using Python 3.4) I've had failures in the 'patch' tests, for example:
..........FFF.F.
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FAIL: test_patch_alter_value (test_core.TestCore)
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Traceback (most recent call last):
  File "/Users/francescopischedda/works/warlock/test/test_core.py", line 173, in test_patch_alter_value
    '[{"path": "/name", "value": "Finland", "op": "replace"}]')
AssertionError: '[{"op": "replace", "path": "/name", "value": "Finland"}]' != '[{"path": "/name", "value": "Finland", "op": "replace"}]'
- [{"op": "replace", "path": "/name", "value": "Finland"}]
+ [{"path": "/name", "value": "Finland", "op": "replace"}]

to prevent this I've changed the tests to compare objects instead of strings