add spaces on blank lines to keep mustache from killing them. closes #26

authority/server/prove_template.txt

 Hello {{email}},
-
+ 
 This message is being sent to you because someone is trying to log
 into a site using this email address.  If you are presently logging
 into a website using BrowserID, then click the link below to complete
 your login:
-
+ 
 {{link}}
-
+ 
 If you are NOT trying to log into a website, just delete this email.
-
+ 
 Sincerely,
 BrowserID (A better way to login)