Add Contributors file
remove Methods and Options map from ApiStruct
Use net/url vor baseUrl and QueryValues
remove unused global
Simplify by usung r.SetQuery()
use httptest.Sever for testing
replaced tests against httpbin.org with httptest server

unearthed an error in Id("delete",r), where another / is appended to the base url
just use a single test server
using bitly's simplejson to handle complex, dynamic json responses
fixed tests
remove variadic interfaces where we don't need them