Change logs:
Code has been refactored. Each dimension uses the same set of code.
A few automated tests have been written.
Functions now include docstrings.
Lower dose cut off only removes those doses that are lower than the value given. Before it would remove the value given and all those below.
Maximum test distance now defaults to np.inf. User now needs to explicitly define maximum test distance for it to come into effect.
In regions where gamma was not calculated np.nan is returned. Previously np.inf was returned.
An extra row and point was added so that no checked points are ever larger than the step size.