Pylinkage

- When linkage animation was saved, last frames were often missing in
``pylinkage/visualizer.py``, function ``plot_kinematic_linkage``.

- ``README.md`` could not be seen in PyPi.
- Various types

- ``circle`` method of ``Pivot`` in ``pylinkage/linkage.py``. It was causing errors
- ``tox.ini`` now fixed.

- ``.gitignore`` Python Package specific extensions added
- ``MIT License`` → ``LICENSE``
- ``lib/`` → ``pylinkage/``
- ``tests/`` → ``pylinkage/tests/``
- Revamped package organization.
- Cleared ``setup.py``

- ``lib/geometry.py`` as a mathematical basis for kinematic optimization
- ``lib/linkage.py``, linkage builder
- ``lib/optimizer.py``, with Particle Swarm Optimization (built-in and PySwarms),
and exhaustive optimization.
- ``MIT License``.
- ``requirements.txt``.
- ``setup.py``.
- ``tests/__init__.py``.
- ``tests/test_geometry.py``.
- ``tests/test_linkage.py``.
- ``.gitignore``.