Multilanguage support

[erlapso]

The Forecast API provides support for different locales, now included in the module. README updated accordingly

[mateodelnorte]

Thanks for the push. Much appreciated.

Please ensure that all the tests run. The update breaks the following:

  1) Forecast #get should be able to specify multiple options via options param:
     Uncaught AssertionError: expected { code: 400, error: 'An invalid units parameter was provided.' } to have property currently
      at Assertion.prop.(anonymous function) [as property] (/Users/matt/development/forecast.io/node_modules/should/lib/should.js:61:14)
      at /Users/matt/development/forecast.io/test/index.js:66:26
      at Request._callback (/Users/matt/development/forecast.io/index.js:62:7)
      at Request.self.callback (/Users/matt/development/forecast.io/node_modules/request/request.js:237:22)
      at Request.emit (events.js:98:17)
      at Request.<anonymous> (/Users/matt/development/forecast.io/node_modules/request/request.js:1146:14)
      at Request.emit (events.js:117:20)
      at IncomingMessage.<anonymous> (/Users/matt/development/forecast.io/node_modules/request/request.js:1097:12)
      at IncomingMessage.emit (events.js:117:20)
      at _stream_readable.js:943:16
      at process._tickCallback (node.js:419:13)

Write a test for the new code as well, if you could.

Thanks!