Multiple API Keys?

What would you think about changing the API for this gem to one where you'd create an instance of an object with your API key and operate from there, rather than setting it on the module? I generally tend towards this pattern because it allows people to, for whatever reason, use two (or more) different API keys in the same program. I'm envisioning something like this:

``` ruby
congress = Sunlight::Congress.new('lolthisisnotarealkey')

congress.legislator.by_zipcode("90210")
# => [#<Sunlight::Congress::Legislator:0x007fad4a2f67b0 @first_name="Henry"...
```

Totally understand if this isn't the direction you want to take. Just throwing it out there. Obviously, this would warrant a major version rev, which is sort of weird for a newish gem.