Added methods into Assignment and AssignmentCategory to compute average grades
Merge pull request #1 from VanGrack/course_statistics

Added methods into Assignment and AssignmentCategory to compute average grades
Merge pull request #34 from VanGrack/master

Added methods into Assignment and AssignmentCategory to compute average grades
removing ghostGraderBook
rename interface to interfaces
Add openfile.java and loadXML.java into io
Merge pull request #36 from LilongHuang/lilongBranch

Fixing UI
Merge pull request #5 from spockNinja/master

11/1