Implemented automatic source parameter settings

- Fixes #6 when 'Hand' or 'Lung' are selected, otherwise the user is
asked to input the kV and mAs.
- Switched from inputting mA to mAs, since the total dose (mAs) is
  given, we can only change the mA and source exposure time.
- Cleaning up output
- HarMoNizinG CapiTaliZatioN Of variaBle namES
- It's always good to run `pep8`