updates to readMilleBinary.py script

While these two updates aren't really related, I am keeping them in the same issue since I plan to resolve them both with on Merge Request.

Planned Updates

There are two updates I would like to make to the mille binary python script.

Python3

I'd like to update the script to be functional for both python2 and python3. On some systems I use, python3 is the default python and so I have had to modify the script for it to be able to run.

Corruption Testing

In some cases, a mille binary file gets corrupted. This is usually not caused by Millede-II or GBL, but instead an outside factor like a copying issue on a distributed filesystem. For this reason, I would like to add an option to the script that will not print the data and instead just scan the file checking that it has the correct format. This will be used to make sure that a mille binary file is not corrupted and does not need to be re-generated before being provided to pede.

Sidenote: Is there a location in the Millepede-II wiki documenting the binary file format? If not, I expect I will learn more about the format during this development and will offer to update the wiki with my notes.