Update Weather script to support "natural language" replies, specify temperature format

[mbmccormick]

The Weather script now uses a more "natural" format for it's replies. You can now interact with Hubot for weather like this for current conditions:

Me: weather in Seattle
Hubot: Currently in Seattle, WA it is Partly Cloudy and 48ºF with a humidity of 71%.

Or like this for forecast:

Me: forecast for Seattle
Hubot: The forecast for Seattle, WA is as follows:

Tue: Clear with a high of 54ºF and a low of 38ºF.
Wed: Rain with a high of 52ºF and a low of 41ºF.
Thu: Showers with a high of 52ºF and a low of 40ºF.
Fri: Chance of Rain with a high of 49ºF and a low of 41ºF.

And if something goes wrong, Hubot will do this:

Me: weather
Hubot: Sorry, but I couldn't find that location.

Users can now specify what format they would like to receive their weather information in. By default, Hubot will use Fahrenheit format for temperatures. However, by specifying the HUBOT_WEATHER_CELSIUS environment variable, Hubot will respond with temperatures in Celsius.