Release v0.5.0

[jonseitz]

New Features

• Create useConfirm hook to warn about discarding unsaved changes (closes seas-computing/course-planner#419)
• Create GlobalMessage for top-level app notifications (closes seas-computing/course-planner#369)
• Create TextArea form component (closes seas-computing/course-planner#452)
• Create Popover component (closes seas-computing/course-planner#495)

Bug Fixes

• Clean up padding of DropdownListItem component (fixes seas-computing/course-planner#515)
• Add form prop to button component (Fixes #132 -- Thanks @sonusindhu)
• Export Props interface for DropdownOptions (fixes seas-computing/course-planner#532)
• Fix modal closing bug when clicking-and-dragging inside text fields (fixes seas-computing/course-planner#538)
• Remove node-canvas dependency to fix arm support in Course Planer (See seas-computing/course-planner #455)
• Add aria-selected active to TabListItem (fixes seas-computing/course-planner#247)
• Improve color contrast of error message (fixes seas-computing/course-planner#598)
• Set consistent heading between TableRowHeadingCell and TableCell (fixes seas-computing/course-planner#602)