Clarify the email field in the registration form.

r2/r2/public/static/css/reddit.css

@@ -2016,6 +2016,10 @@ li.searchfacet {
     color: #606060; 
 }
 
+.user-form label.note {
+    font-weight: normal;
+}
+
 .user-form .error {
     margin-left: 5px;
 }

r2/r2/templates/login.html

@@ -78,10 +78,11 @@
       %if register:
         <li>
           <label for="email_${op}">
-            ${_('email')}: &nbsp;<i>(${_('optional')})
+            ${_('account recovery email')}: &nbsp;<i>(${_('optional')})
           </i></label>
           <input value="" name="email" id="email_${op}" 
                  type="text" maxlength="50" tabindex="${tabindex}"/>
+          <label for="email_${op}" class="note">${_('we will only send email at your request')}</label>
           %if register:
             ${error_field("BAD_EMAILS", "email", kind="span")}
           %endif