Use Gitter notifications

* Added a webhook notification for Gitter notifications.
   * Disabled email notifications because @yorik's configuration
     effectively did that but setting email to false is shorter

.travis.yml

@@ -46,11 +46,13 @@ git:
   depth: 5000
 
 notifications:
-  email:
-    recipients:
-      - yorik@uncreated.net
-    on_success: never
-    on_failure: never
+  email: false
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/479456663cdf5c84e4d8
+    on_success: always
+    on_failure: always 
+    on_start:   change
 
 before_install:
 - eval "$(curl -fsSL "https://raw.githubusercontent.com/${OSX_PORTS_CACHE}/v${FREECAD_RELEASE}/travis-helpers.sh")"