Change duration.toIsoString to duration.toISOString. Closes #1752
deprecate pre-2.0 add/subtract
Simplify readme

 * Move the changelog to its own file
 * Make badges look like moment-timezone
Move readme simplification

 * Rename readme.md to README.md because apparently that's the cool
 thing to do
 * Move more stuff into contributing.md.
 * Make CONTRIBUTING.md a little less yelly because the default branch
 thing seems to be working.
more simplification
Merge pull request #1759 from icambron/iso_vs_ISO

Change duration.toIsoString to duration.toISOString

@changelog
@section deprecation
@description rename duration.toIsoString to duration.toISOString
fixed spelling
Merge pull request #1765 from icambron/simplify_readme

Simplify readme
deprecate pre-2.0 add/subtract
fix todo
cleanup
Merge pull request #1763 from icambron/add_subtract_order

deprecate pre-2.0 add/subtract
s/lang/locale

 * Deprecated moment.lang(), moment.langData(), moment#lang, and
 duration#lang

 * Added moment.locale(), moment.localeData(), moment#localeData, and
 druation#localeData

 * Added moment.defineLocale() that defines a locale but doesn't set it
 as the global locale (#1750)

 * Removed the hack in the language concatenator that set the language
 to English.

 * Refactored internal code to use moment#localeData instead of local
 functions, and set the language directly on the moment instance at
 creation.

 * Moved all the files and changed the build scripts so that everything
 lives is named "locale" instead of "lang", e.g. the locale files under
 the "locale" directory.

 * I did *not* include build-generated changes like component.json and
 the concated locale files, but I did inspect them to see that they look
 right.
incorporating ichernev comments
my support
Merge pull request #1778 from gholadr/develop

Myanmar localization
Added Afrikaans translation
Update af.js
Added Afrikaans language test file
Merge pull request #1786 from wernerm/develop

Added Afrikaans translation