Use modules @next instead of @rc

Author: dtopuzov

core/tns/tns.py

@@ -19,7 +19,7 @@
 class Tns(object):
     # npm tag used when we publish master branch of https://github.com/NativeScript/NativeScript
     # Please see https://github.com/NativeScript/NativeScript/blob/master/.travis.yml
-    NEXT_TAG = 'rc'
+    NEXT_TAG = 'next'
 
     @staticmethod
     def __get_platform_string(platform=Platform.NONE):