ci: push build only master

Author: radeva

.travis.yml

@@ -1,3 +1,6 @@
+branches:
+  only: 
+    - master
 env:
   global:
     - ANDROID_PACKAGE='demo-debug.apk'
@@ -91,4 +94,4 @@ cache:
 install:
     - npm install -g nativescript
     - tns usage-reporting disable
-    - tns error-reporting disable
+    - tns error-reporting disable