Move new assertions to separate file.
Make default get_standard_message work for more cases.
Convert Assert arguments to an context object.
Move assertSequenceEqual to a separate class.
Minor AssertSequenceEqual refactor.
Introduce Assert.fail method.
Move assertIsInstance to separate class.
Move assertDictEqual to separate class.
fixup
s/standardMsg/standard_message/g
s/_formatMsg/_format_message/g
s/_truncateMessage/_truncate_message/g
PEP-8 the assertion_context field names.
Minor cleanup.
Switch to .format for messages, as we don't need to worry about Python 2.
Replace string interpolation with .format throughout.
Refactor AssertSequenceEqual.test.
s/standard_message/failure_description/g
Push diff truncating entirely in to Assert super-class.
Move assertCountEqual to separate class.