-Python 2.7 support dropped.
Python 3 has a number of features that Python 2 does not,
and because this project is just getting started, I didn't want to support Python 2,
and then eventually drop it as Python 3 becomes more and more mainstream.
-Internal overhaul.
Modules are now in the root folder.
A core module with specialized submodules was created with a number of various tools.
-Demo files were assimilated into one directory with respective subdirectories.
-VMAT module can now handle HDMLC images.
-CBCT module was restructured and is much more reliable now.
-method names normalized, specifically the `return_results` method, which had different names
in different modules.
-Lots of tests added; coverage increased dramatically.