Merge pull request #9 from tarzzz/Shape-and-subclasses

Shape and subclasses
Modified some tests for __str__()
Modified some tests for shapes __str__()
Merge pull request #10 from tarzzz/tests-shape-modifications

Modified some tests for __str__()
Added generate_dict method for Shape class
Added tests for Shape class
Merge pull request #11 from tarzzz/test-Shape-class

Test shape class
Modified Cylinder tests
Added Cylinder, Cube classes , tests all pass
Merge pull request #12 from tarzzz/tests-cylinder-modifications

Modified Cylinder tests
Added Cone, Sphere, Circle and Plane Shapes
Minor Error correction in tests
Added Tetrahedron, Octahedron, and Icosahedron classes
Modified some errors on Octahedron tests. Issue with the strings
Added Torus Shape
Changed according to PEP8
Added TorusKnot Shape
Merge pull request #13 from tarzzz/tests-cylinder-modifications

Minor Error correction in tests
Merge branch 'master' of https://github.com/PythonDynamics/pydy-viz into Shape-and-subclasses

Conflicts:
	pydy_viz/tests/test_shapes.py