Rewriting of links for Course Updates and Course Handouts.

STUD-669.
Slightly change email registration template
    Added some text to guide the student to register with a particular email address.
    This is the one that was entered into the enrollment/invitation form by the instructor.
    Modified the template and associated test.
Merge pull request #827 from edx/christina/course-info-links3

Rewriting of links for Course Updates and Course Handouts.
Instrumented course email for DataDog
Merge pull request #834 from edx/dcadams/fix_email_registration_template

Small change to email registration template
Kill processes after running rake
Merge pull request #831 from edx/will/statsd-bulk-email

Instrument course email for DataDog
Merge pull request #838 from edx/fix/kill-rake-processes

Kill processes after running rake