Adding hooks for external libs to supply timezone name and timezone abbreviations

[timrwood]

This is to allow libs like moment-timezone and others to provide timezone information by overwriting moment.fn.zoneName and moment.fn.zoneAbbr.

[ichernev]

I think this version should also print the local timezone. Where to get it with this (new Date()).toString().match(/\((.*)\)/)[1]. It can be cached once the library is loaded.

[timrwood]

Well, the local timezone could be PDT or PST based on DST, so we should probably use the version that was deprecated with #162.

Basically just undo 9b56710, but in moment.fn.zoneAbbr.

[ichernev]

So the moment-timezone will be distributed separately, and you can use moment without it? Also -- if you have any moment, you can get the Date and extract the timezone, no matter what the DST is now (or was at some point). So I guess it won't be cached, but it would still be correct. We can fallback to GMT/UTC+-NNNN if we can not extract anything, that would still provide a timezone specifier, maybe not very compact but at least not wrong.

[timrwood]

Actually, now that I think about it, it's probably best not to add support for timezone abbreviations in the core lib.

As noted in #162, browser support for getting the timezone name is very inconsistant, even inconsistent across different timezones.

The good thing is that adding these hooks will make it easier for someone to take a library like jstimezonedetect and add a moment.js hook for getting the timezone name.

We could even add a link to a gist that adds support for getting timezones based on the Date.prototype.toString hack, but I think it's too buggy to be a part of the core lib.

[ichernev]

Well. then the only thing that needs to be part of the core lib is the z/zz format tokens, because the functions can be added by any plugin anyway. And if that's the case I'd think about a generic way of adding format (and maybe parse) tokens through plugins.

[mattjohnsonpint]

Tim, one thing that would help is if you could please be consistent in terminology. When I hear the terms "zone" or "time zone", I think of a named time zone like America/New_York. When I see a value like -04:00, I prefer to call that an "offset" to avoid confusion. Since many zones have multiple offsets, it gets confusing when these terms get mixed up. In wrote this up as "TimeZone != Offset" as part of the TimeZone tag wiki on StackOverflow. Thanks.