Added weather method to entry object

I added a `weather` method to the entry object. The `weather` method simply prints out the temperature and weather description. The `weather` method takes one parameter, `'c'` if you want Celsius and `'f'` if you want Fahrenheit. Though all this information is accessible through the entry dictionary, I thought it would be useful to print it out in one string (much like location).

I ran the tests and everything passed.