Added Cylinder, Cube Shape
Modified __init__ to make length and radius as optional args in Cube/Cylinder
Added import statement for mechanics
Added import statements, corrected for PEP8
Added generate_dict method for Shape class
Added Cylinder, Cube classes , tests all pass
Added Cone, Sphere, Circle and Plane Shapes
Added Tetrahedron, Octahedron, and Icosahedron classes
Added Torus Shape
Added TorusKnot Shape
Merge branch 'master' of https://github.com/PythonDynamics/pydy-viz into Shape-and-subclasses

Conflicts:
	pydy_viz/tests/test_shapes.py
WIP Added Torus Geometry,
WIP Mesh Shape
Modified some VisualizationFrame tests
Added Cyliner instead of mesh shape
Completed all Shape classes. Modified one test for numerical error
Replaced mesh_shape with shape
Added non-trivial numerical values for tests.
removed * imports.
Changed Shape from mesh to Cylinder
Removed Shape from optional arg
1) Removed delete frames method
2) changed __init__ method
3) wrote some docstrings