Update moment.js to 2.6.0

From: https://github.com/moment/moment/commit/37808f3f9dec14e37ad2b5cff45c70f63b021d17

Bug: 63873
Change-Id: I471c0e47243b10b2db9367079e7e9c86995d5ef8
Merge "Update moment.js to 2.6.0"