Support translate empty string

[QingWei-Li]

No description provided.

[coveralls]

Coverage increased (+0.2%) to 91.553% when pulling 6df0b2f on QingWei-Li:feat/translate-empty-string into 2bfe9fd on kazupon:dev.

[kazupon]

Thank you for your Pull Request.

However, I can't understand empty string translation in use-cases.

Can you tell us the your specific content please?

[QingWei-Li]

Reason 1:
Due to linguistic differenes, one may need this feature when implementing i18n to a common component.

Let's say I'm building a Date Picker. For Chinese users I need to display:

2016 年 11 月

For English users, it should be

2016 November

So the config may look something like this:

// for Chinese
{
  year: '年',
  month11: '11 月'
}

// for English
{
  year: '',
  month11: 'November'
}

Reason 2:
If a user configs a void string, basically he just want to show a void content, but now vue-i18n displays a key path. I think it's not quite what the user actually anticipates.

[kazupon]

okay, it makes sense. :)

[QingWei-Li]

thx 😄