Final Webhook Management API Changes

- Updated Samples
- Additional Functional Tests
- Enabled Travis to do functional tests (with allowed failures) on each build

.travis.yml

@@ -5,9 +5,13 @@ php:
   - 5.5
   - 5.6
   - hhvm
+env:
+  - REST_MODE=mock
+  - REST_MODE=sandbox
 matrix:
   allow_failures:
     - php: hhvm
+    - env: REST_MODE=sandbox
   fast_finish: true
 before_script:
   - composer self-update