Major update, primarily to add pagination support.

* Added Reference objects to encapsulate API calls.
* Added Result objects to encapsulate API responses.
* Changed the return value of APIClient#execute to Result.
* Changed the method signature of APIClient#execute to support named params.
* Added APIClient#execute! which throws exceptions on error.
* Added automatic parsing code to better allow for complex nested structures.
* Added error parser.
* Added module for pagination in parsers.

examples/buzz.rb

@@ -75,10 +75,10 @@ get '/oauth2callback' do
 end
 
 get '/' do
-  response = @client.execute(
+  result = @client.execute(
     @buzz.activities.list,
-    'userId' => '@me', 'scope' => '@consumption', 'alt'=> 'json'
+    {'userId' => '@me', 'scope' => '@consumption', 'alt'=> 'json'}
   )
-  status, headers, body = response
-  [status, {'Content-Type' => 'application/json'}, body]
+  status, _, _ = result.response
+  [status, {'Content-Type' => 'application/json'}, JSON.generate(result.data)]
 end