Update AUTHORS and CHANGELOG for libaom v3.1.0

It is not necessary to tweak .mailmap to remove duplicates.

BUG=aomedia:3028

Change-Id: I103626bc53a3c3bb99171fd3eed3e39379af7404
diff --git a/AUTHORS b/AUTHORS
index bb0acb7..d8711a6 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -36,6 +36,7 @@
 Charles 'Buck' Krasic <ckrasic@google.com>
 Cheng Chen <chengchen@google.com>
 Cherma Rajan A <cherma.rajan@ittiam.com>
+Chethan Kumar R E <chethan.kumar@ittiam.com>
 Chi Yo Tsai <chiyotsai@google.com>
 Chm <chm@rock-chips.com>
 Christian Duvivier <cduvivier@google.com>
@@ -166,6 +167,7 @@
 Mirko Bonadei <mbonadei@google.com>
 Monty Montgomery <cmontgomery@mozilla.com>
 Morton Jonuschat <yabawock@gmail.com>
+Mudassir Galagnath <mudassir.galaganath@ittiam.com>
 Mufaddal Chakera <mufaddal.chakera@ittiam.com>
 Nathan E. Egge <negge@mozilla.com>
 Neil Birkbeck <birkbeck@google.com>
@@ -232,6 +234,7 @@
 Tamar Levy <tamar.levy@intel.com>
 Tao Bai <michaelbai@chromium.org>
 Tarek AMARA <amatarek@justin.tv>
+Tarundeep Singh <tarundeep.singh@ittiam.com>
 Tero Rintaluoma <teror@google.com>
 Thijs Vermeir <thijsvermeir@gmail.com>
 Thomas Daede <tdaede@mozilla.com>
@@ -249,6 +252,7 @@
 Victoria Zhislina <niva213@gmail.com>
 Vignesh Venkatasubramanian <vigneshv@google.com>
 Vishesh <vishesh.garg@ittiam.com>
+Vishnu Teja Manyam <vishnu.teja@ittiam.com>
 Vitalii Dziumenko <vdziumenko@luxoft.com>
 Vitalii Dziumenko <vdziumenko@luxoft.corp-partner.google.com>
 Wan-Teh Chang <wtc@google.com>