Fixed email text overflow in proposal#show

Email icon is used solve email text overflow.
Fixes #1838

app/views/proposals/show.html.haml

@@ -36,8 +36,10 @@
             .col-md-8
               %h4
                 = link_to speaker.name, user_path(speaker.id)
+                %br
                 - if speaker.email_public?
-                  = "(#{speaker.email})"
+                  = mail_to "#{ speaker.email }" do
+                    %i.fa.fa-envelope-o.fa-2x
               - if speaker.affiliation?
                 .text-muted
                   from