Update grammar.md
Update grammar.md

tjmonsi/cmsc129-2016-repo,tjmonsi/cmsc129-2016-repo,tjmonsi/cmsc129-2016-repo,tjmonsi/cmsc129-2016-repo,tjmonsi/cmsc129-2016-repo,tjmonsi/cmsc129-2016-repo,tjmonsi/cmsc129-2016-repo