Issue 4849: Update NOTICE (#4850)
Issue 4849: Update NOTICE (#4850)

Updates NOTICE file with the year range 2017-2020.

Signed-off-by: Flavio Junqueira (fpj) <3143f522c4835f95078812226e7dab45695d0369@apache.org>
pravega/pravega,pravega/pravega,pravega/pravega