Merge pull request #4 from AICC/master

Update
Update cmi5_runtime.md

formatting
Update cmi5_runtime.md
Update cmi5_runtime.md
Update cmi5_runtime.md

AU definition updated to reference Learning Activity Provider per the March 15th Meeting
Merge pull request #22 from MrBillMcDonald/master

Update Assignable Unit Defintion to Include Learning Activity Provider (per March 18th Meeting)