Locale.GetND should return singular default when N=1

[alexedwards]

I'm very new to this package, so sorry if I'm misunderstanding something!

But it seems like the GetND and GetNDC methods in locale.go only return the plural default, not the singular when N=1.

I had quick look through the issues, and it looks like the same problem in the po.go file was fixed in #8, but the corresponding methods in locale.go weren't fixed at the same time.

[leonelquinteros]

@alexedwards I've been looking into this issue, and while it's a bug, the solution is more complex than just N=1.

What's happening here is that the Locale object you're using doesn't have the Domain (Po object) you're requesting loaded, so it defaulted to the plural.
That said, the current implementation was using the n == 1 rule to identify singular cases, and that's kind of incorrect, because it would depend on the plurals definition from the .po file.

So I'm working on a solution in the Po object that will fallback to the corresponding default value based on the plural forms definitions in the .po file.
When it fallbacks to an non-existing translation string, but on an existing domain (.po file) it will use this new approach.
Otherwise, as if the domain isn't loaded and it doesn't knows how plural definitions are, it will fallback using the western n == 1 rule, just to make a convention here.

I'll be pushing a fix to master branch soon.

[alexedwards]

Thanks for the time looking into this and the fast fix. I really appreciate it 👍