Upgrade react-native from 0.29 to 0.31.
Upgrade react-native from 0.29 to 0.31.

kunall17/zulip-mobile,nashvail/zulip-mobile,Sam1301/zulip-mobile,vishwesh3/zulip-mobile,vishwesh3/zulip-mobile,kunall17/zulip-mobile,nashvail/zulip-mobile,vishwesh3/zulip-mobile,Sam1301/zulip-mobile,Sam1301/zulip-mobile,nashvail/zulip-mobile,saketkumar95/zulip-mobile,saketkumar95/zulip-mobile,kunall17/zulip-mobile,nashvail/zulip-mobile,saketkumar95/zulip-mobile,saketkumar95/zulip-mobile,kunall17/zulip-mobile,saketkumar95/zulip-mobile,Sam1301/zulip-mobile,Sam1301/zulip-mobile,vishwesh3/zulip-mobile,Sam1301/zulip-mobile