Remove the urbacon theme.

The yourbacon... I mean urbacon theme is really just a copy of the
simple theme with some color and logo changes. Plus the logo is
likely copyrighted and shouldn't be included under rubycas-server's
MIT license anyway.

public/themes/urbacon/theme.css

@@ -1,33 +0,0 @@
-body {
-  background-image: url(bg.png);
-}
-
-label {
-  color: #5c6156;
-}
-
-#login-form {
-  background-repeat: no-repeat;
-  background-image: url(login_box_bg.png);
-  height: 175px;
-  width: 210px;
-  padding: 20px;
-}
-
-#logo-container {
-  vertical-align: top;
-}
-
-#logo {
-    width: 115px;
-    height: 171px;
-}
-
-#infoline {
-  color: #5c6156;
-  font-size: 8px;
-}
-
-#headline-container {
-  margin-right: 15px;
-}