Merge pull request #16 from sichinumi/master

Annotation min/max/delete
Merge pull request #17 from sichinumi/master

Canvas fixes merged from pongad, partial merge from dustsnow
Merge pull request #18 from sichinumi/master

Fixed grading rubric UI
link done
typo
Added Rectangle & Ellipse Drawing
Merge pull request #20 from Webs961/master

Added shape drawing
Merge attempt
Merge attempt 2
Merge attempt #3