Update Moment.js from 2.7.0 to 2.8.1

Project site

* http://momentjs.com/ and https://github.com/moment/moment/

File source

* https://github.com/moment/moment/blob/2.8.1/moment.js

README

* https://github.com/moment/moment/blob/2.8.1/readme.md

Changelog

1.8.0 changelog

* https://gist.github.com/ichernev/ac3899324a5fa6c8c9b4

1.8.1 changelog

* https://github.com/moment/moment/blob/2.8.1/CHANGELOG.md

difference between 2.7.0 and 2.8.1

incompatible changes

* #1761: moments created without a language are no longer following the global language, in case it changes. Only newly created moments take the global language by default. In case you're affected by this, wait, comment on #1797 and wait for a proper reimplementation
* #1642: 45 days is no longer "a month" according to humanize, cutoffs for month, and year have changed. Hopefully your code does not depend on a particular answer from humanize (which it shouldn't anyway)
* #1784: if you use the human readable English datetime format in a weird way (like storing them in a database) that would break when the format changes you're at risk.
* #1785  moment.momentProperties  is now an array of properties instead of a hash. If you have a plugin that uses it to make sure cloned moments will retain the plugin-added properties you need to change your code.

deprecations (old behavior will be dropped in 3.0)

* #1761  lang  is renamed to  locale ,  langData  ->  localeData . Also there is now defineLocale  that should be used when creating new locales
* #1763  add(unit, value)  and  subtract(unit, value)  are now deprecated. Use  add(value, unit)  and  subtract(value, unit)  instead.
* #1759 rename  duration.toIsoString  to  duration.toISOString . The js standard library and moment's  toISOString  follow that convention.

new locales

* #1789 Tibetan (bo)
* #1786 Africaans (af)
* #1778 Burmese (my)
* #1727 Belarusian (be)

bugfixes

* #1738 local to zone conversion with keepLocalTime=true
* #1642 more accurate humanize

performance

* #1808 speedup cloning 49x
* #1708 speedup creation with Date object

features

*#1716  moment.relativeTimeThreshold  now supports getting the existing threshold

locale bugfix

* #1784 add comma between day-of-month and year in us-en
* #1710 fix lithuanian month name

2.8.1

* bugfix #1813: fix moment().lang([key]) incompatibility

Change-Id: Iaffaaa18e08773f8f36e83e918e61a2259f1e2e3