To begin addressing issue #79, add a letter grade to a Student and persist it in the XML document.
Add the ability to set a student's final grade in the GradeBook Swing UI.
Began to implement a range of scores for letter grades in a grade book.
Added default grade ranges
Throw an exception when a range's maximum value is larger than its minimum value.
Use "minimum" and "maximum" terminology for ranges.
Validate the the ranges include 0 and 100.
Validate that letter grade ranges are contiguous.
Refactor GradeBook XML code so that I can write a failing test that tests that letter grade ranges are persisted.
Broke up the huge dumpGradeBook() method into smaller methods.
Broke up the huge parse() method into smaller methods.
Persist letter grade ranges to XML.
Persist letter grade ranges to XML.
Get the letter grade for a score.
Compute the students letter grade based on the ranges defined in the grade book.
Merge pull request #83 from DavidWhitlock/compute-final-grade

Automatically compute a student's letter grade.

Augment the Student with a "letter grade" and augment the GradeBook with a ranges of scores that correspond to letter grades. This mostly addresses issue #79.