All values are case insensitive. Closes https://github.com/adlnet/xAPI-Spec/issues/498
SHOULD not MUST for previous commit
Addresses https://github.com/adlnet/xAPI-Spec/issues/433
Merge pull request #519 from garemoko/7_6_tidyup

Addresses #433
Merge pull request #516 from garemoko/case-sensitivity

Case sensitivity for values
minor markdown syntax fix
Merge pull request #521 from garemoko/7_2_4_markdownfix

minor markdown syntax fix
Merge pull request #9 from adlnet/master

update from adl master