Merge tag '0.9.8' into develop

0.9.8
more updates from change log to-do list

Added ...
- SemVer adherence (http://semver.org).
- any non-essential files to .gitattributes to make dist lean.
- exceptions for invalid use of entity, action, or ownership.
- definition of keeper to readme.

Changed ...
- back to PSR-4 from PSR-0.
Merge branch 'release/0.10.1'