weather.py, blend.py, new usage of dice.py, refactoring

WHAT I'VE DONE:
* Added weather.py. The user can now type `hey fetch the weather for the area code [7 digit area code] for me` and the current conditions and forecast for the next week will be outputted. weather.py makes use of Yahoo!'s weather API to do this.
* Added blend.py. The user is now capable of blending two colors together using hey. The colors can be given to hey in hexadecimal notation only (at the moment). For example, the user can type `hey blend FF0000 and FFFFFF, as well as AAFF12` and hey will do as it is commanded. Hey will also offer to open up a web browser on colorpicker.com, where the user can see the blended color.
* Added new functionality to dice.py. The new functionality is very basic -- you can now specify the number of sides on the dice which will be rolled. E.g., `hey roll a 23 sided dice for me` or `hey roll a dice that has 64 sides`.
* General refactoring. :)

Cheers! :beers: