Dictdiffer

- Changes order of items for REMOVE section of generated patches when
`swap` is called so the list items are removed from the end. (85)
- Improves API documentation for `ignore` argument in `diff` function.
(79)
- Executes doctests during PyTest invocation.

- Adds support for comparing NumPy arrays. (68)
- Adds support for comparing mutable mappings, sequences and sets from
`collections.abs` module. (67)
- Updates package structure, sorts imports and runs doctests.
- Fixes order in which handled conflicts are unified so that the
Merger's unified_patches can be always applied.

- Adds tolerance parameter used when user wants to treat closed values
as equals
- Adds support for comparing numerical values and NaN. (54) (55)

- Adds support for diffing and patching of sets. (44)
- New tests for diff on the same lists. (48)
- Fix for exception when dict has unicode keys and ignore parameter is
provided. (50)
- PEP8 improvements.

- Adds ignore argument to `diff` function that allows skipping check
on specified keys. (34 35)
- Fix for diffing of dict or list subclasses. (37)
- Better instance checking of diffing objects. (39)

- Fix for empty list instructions. (30)
- Regression test for empty list instructions.