Added view for editing GradingRecords.
This view shows a list of GradingRecords if the id param is not present in the GET data.
Also renamed grading_record to view_records and fixed the redirect for that page
to also point to the GradingRecord edit page.
Coverage: code coverage testing for Python
Coverage.py is a Python module that measures code coverage during test execution.
It uses the code analysis tools and tracing hooks provided in the Python standard
library to determine which lines are executable, and which have been executed.
For more information, see http://nedbatchelder.com/code/modules/coverage.html