Default to using "http:" protocol in http adapter
Default to using "http:" protocol in http adapter

Fixes #490

renzhaozhao/axios,akshatnitd/axios,renzhaozhao/axios,renzhaozhao/axios,akshatnitd/axios,akshatnitd/axios,axios/axios,mzabriskie/axios,mzabriskie/axios,axios/axios,mzabriskie/axios,axios/axios