Unittests

Add unittest for project which can be run using
```
python3 setup.py test
python2 setup.py test
```
Note that 434e68b588 broke the tests which were passing prior to this

It also seems that `TestEquation` should return `0.149877209662952` according to https://www.wolframalpha.com/input/?i=sin%283%2B4^2%29

I suggest merging this request and changing the value to the correct one before fixing calculation issue.