Nano-utils

*****
* Updated the development status from Beta to Production/Stable.

*****
* Added the ``nanoutils.testing_utils`` module;
contains the ``FileNotFoundWarning`` class and ``delete_finally()`` decorator.

*****
* Set the default output of ``AbstractFileContainer.write()`` to ``sys.stdout``.
* Cleaned up ``tests_require`` in ``setup.py``.
* Added the ``get_func_name()`` function.
* Added the ``module`` argument to ``issubclass_factory()``, ``isinstance_factory()``
and ``import_factory()``.
* ``PartialPrepend`` and ``SetAttr`` are now in their own (private) modules.
Note that they still should be imported from (preferably) ``nanoutils`` or
otherwise ``nanoutils.utils.
* Run tests on the ``docs/`` directory.
* Updated annotations and documentation.
* Fixed an issue where decorator documentation wasn't properly generated.

*****
* Minor documentation fixes.
* Added the ``ignore_if()`` decorator.

*****
* Added the ``AbstractFileContainer`` class and ``file_to_context()`` function.
* Marked all internally used type annotations are private.
* Added `contextlib2 <https://github.com/jazzband/contextlib2>`_ as a dependency for Python 3.6.

*****
* Added ``PathType``, an annotation for `path-like <https://docs.python.org/3/glossary.html#term-path-like-object>`_ objects.
* Added the ``copy`` argument to ``as_nd_array()``.