Add more tests for inverse kinematics edge cases

[mithi]

related to #73

Checkout sample test case:

• https://github.com/mithi/hexapod/blob/master/src/tests/cases/ikSolver/case1.js

and how it's called

• https://github.com/mithi/hexapod/blob/master/src/tests/ikSolver.test.js

Some edges cases to test are listed here

• https://github.com/mithi/hexapod/blob/master/src/hexapod/solvers/ik/HexapodSupportCheck.js
• https://github.com/mithi/hexapod/blob/master/src/hexapod/solvers/ik/IKInfo.js

You might also want to checkout the modules themselves:

• https://github.com/mithi/hexapod/tree/master/src/hexapod/solvers/ik

To have an idea on what kinds of tests to make.

Ideas are welcome.

Thanks!

[mithi]

VirtualHexapod

https://codecov.io/gh/mithi/hexapod/src/master/src/hexapod/VirtualHexapod.js
_handleComplexTwist(verticesList) will be invoked when a more complex kinematics case is used
These blocks of code will be covered as well:
https://codecov.io/gh/mithi/hexapod/src/master/src/hexapod/solvers/twistSolver.js

Inverse Kinematics Edge Cases

https://codecov.io/gh/mithi/hexapod/src/master/src/hexapod/solvers/ik/LinkageIKSolver.js
https://codecov.io/gh/mithi/hexapod/src/master/src/hexapod/solvers/ik/IKSolver.js
https://codecov.io/gh/mithi/hexapod/src/master/src/hexapod/solvers/ik/HexapodSupportCheck.js

[mithi]