Merge pull request #18 from adlnet/master

Syncing
homePage fix, StatementRef UUID fix, Identified Group table fix

Updated inconsistent homepage to homePage (1 occur)
Clarified StatementRef UUID requirements (2 occur)
Updated Identified Group table to be consistent with requirement (1 occur)
Update xAPI.md
Update xAPI.md
Merge pull request #321 from andyjohnson/master

homePage fix, StatementRef UUID fix, Identified Group table fix