shields.io: review use

[odscjames]

• Python version info is missing; not sure what we need, maybe classifiers in setup?
• Shields.io info is always from latest released pypi version and thus can be misleading. For instance in the future, when we have released several more versions, a user looking at an old version delibrately (eg https://github.com/Open-Telecoms-Data/lib-cove-ofds/tree/v0.7.0 ) will see the version as wrong, and may see a different set of python versions from what that release actually supports.