add locale(s) support

[hhsnopek]

Tests:

• setup
• global locales
• scope locale
• locale_prefixes

closes #35

[kylemac]

can we document the new locales interface in the readme too

[kylemac]

@hhsnopek can we implement this with the malala project (needs locales support) this week to put this to the true test?

[zspecza]

Is there any feedback from your malala test? Since this has a 0.10 tag I'm assuming I should include these changes in #55. I noticed that the tests here only fail because of a timeout - looks fairly stable otherwise. /cc @kylemac @hhsnopek

[hhsnopek]

I haven't heard anything from the malala test - but if the api doc's are right, it should work as expected