Adding project foreign key to references
Fixed problem of inconsistence of references
Add test for sequences.
Minor cosmetic fixes on pytest integration tests.
Add tests for project automatic sequence create/delete operations.
Fixed references api on task resolution
Remove code from self destroy drf mixin related to pre/post hooks.

Because drf now has support for them.
Some refactoring on mdrender
Improving coverage of mdrender to 100%
Adding render_and_extract function to mdrender service
Flake8 corrections
Removing list_of_milestones from project api
Pytest mutable object fixture.

Usage:
        def test_something(object):
            # mutate object as needed
Creating reusable "filter_by_tags" function.

Moving the filtering-by-tag logic out of TagsFilter into a reusable function.
Turning off signals dispatch when testing units

Model signals pre_save and post_save will be turned off when running
unit tests because they are interfering with the tests.
Automatically skip slow tests

You can mark a test as slow using:

    @pytest.mark.slow
    def test_something():
        ...

Use the option "--runslow" to tell the test runner to also include slow
tests:
        py.test --runslow ...
Moving neighbors logic into standalone module