Update readme with Apache2 license

Author: benmarten

README.md

@@ -109,9 +109,7 @@ You can see more at https://www.leanplum.com/dashboard#/5019738286063616/help/do
 - 1.0.1 Added an option to turn off realtime updates in development mode. Load cached values immediately after calling Start instead of when the API call finishes.
 - 1.0.0 Initial release.
 ## License
-© 2017 Leanplum, Inc. All rights reserved.
-
-You may not distribute this source code without prior written permission from Leanplum.
+See LICENSE file.
 
 Leanplum does not support custom modifications to the SDK, without an approved pull request. Please send a pull request if you wish to include your changes.