use an image for sending an invitation

git-svn-id: http://svn.barleysodas.com/barleysodas/trunk@128 0f7b21a7-9e3a-4941-bbeb-ce5c7c368fa7

app/views/invitations/_invitations.rhtml

@@ -1,2 +1,2 @@
 You have <strong><%= pluralize(@people.invitations.size, 'Invitations') rescue '0 Invitations' -%></strong>.
-<% if @people and !@people.invitations.empty? -%><br /><%= link_to_function 'Send Invitation', "lightboxes['invitation_dialog'].open()" -%><% end -%>
+<% if @people and !@people.invitations.empty? -%><br /><%= link_to_function "#{image_tag('mail-forward.png')} Send Invitation", "lightboxes['invitation_dialog'].open()" -%><% end -%>