Merge pull request #215 from MITx/dormsbee/email_messages

Changing email messages to be edX, even the ones I don't think will be sent

lms/templates/emails/activation_email.txt

-Someone, hopefully you, signed up for an edX account using this 
-email address. If it was you, and you'd like to activate and 
-use your account, copy and paste this address into your web
-browser's address bar:
+Thank you for signing up for edX! To activate your account, 
+please copy and paste this address into your web browser's
+address bar:
 
 % if is_secure:
   https://${ site }/activate/${ key }

lms/templates/emails/welcome_body.txt

-MITx's prototype offering, 6.002x, is open. To log in, visit
+edX has launched! To log in, visit:
 
 % if is_secure:
- https://6002x.mitx.mit.edu
+ https://edx.org
 % else:
- http://6002x.mitx.mit.edu
+ http://edx.org
 % endif
 
-where you will find a login button at the top right-hand corner of the
-window.
+A login button will be at the top right-hand corner of the window.
 
 Please make sure you're using the latest version of Google Chrome or
 Firefox. If you've forgotten your password, the log-in form has a
 place to reset it.
 
-Once you log in, we recommend that you start the course by reviewing
-the "System Usage Sequence" in the Overview section, and the "6.002x
-At-a-Glance (Calendar)" handout under the Course Info tab. After you
-familiarize yourself with the features of the MITx platform,
-you can jump right into the coursework by working on "Administrivia
-and Circuit Elements", the first Lecture Sequence in Week 1.
-
 Thanks for joining us for the ride!
 
-The 6.002x team
+The edX team
 
 (Please note that this e-mail address does not receive e-mails --
 if you need assistance, please use the help section of the web

lms/templates/emails/welcome_subject.txt

-Welcome to 6.002x!
+Welcome to edX!