Enhancements before publication

[AnthonyOfSeattle]

Before version 1.0.0, which will be the first version to appear alongside publication, I want to make the following improvements to the repository.

1. Convert to modern python package design and upload to python package index.
   Currently, I am using an older setup for a python package which I think makes it difficult to control compilation
   and submit to the python package index. I would like to improve the package meta data and submit to PIP so
   that users don't need to go through the drawn out compilation process on Linux or Mac.

2. Enhance ModifiedPeptide class to be a natural python iterator
   Right now, the ModifiedPeptide class lacks a lot of the things that I would like to see in a good python iterator.
   I would like to get this class working as smoothly as possible in python, with options over precisely which ions
   are returned (site determining or not).