Added an email submission processor for extracting the koans submissions to address issue #67.
Write koans attachment to a directory for the student.  Unlike the project submissions, we don't know the id of the student.
Record the time at which the student submitted the koans project.  Be smart about finding the student in the grade book based on the "from" header in the email.
Save the attached file into a directory named for the student id of the sender of the email.  Name the saved file after the student's id, also.
Merge pull request #68 from DavidWhitlock/extract-koan-submissions

Address issue #67 by extracting the submissions in the "koans" email folder into directories and files whose name correspond to the student who submitted the project. The time at which the email was sent is recorded in the grade book.