adding gitter notifications

.travis.yml

@@ -1,2 +1,10 @@
 language: csharp
-solution: B2Uploader.sln
+solution: B2Uploader.sln
+
+notifications:
+  webhooks:
+    urls:
+      - https://webhooks.gitter.im/e/8518132190fd79d798fd
+    on_success: change  # options: [always|never|change] default: always
+    on_failure: always  # options: [always|never|change] default: always
+    on_start: never     # options: [always|never|change] default: always