Add Httpretty to dev requirements
Add Httpretty to dev requirements

erinspace/scrapi,mehanig/scrapi,jeffreyliu3230/scrapi,ostwald/scrapi,CenterForOpenScience/scrapi,alexgarciac/scrapi,icereval/scrapi,felliott/scrapi,CenterForOpenScience/scrapi,fabianvf/scrapi,fabianvf/scrapi,erinspace/scrapi,felliott/scrapi,mehanig/scrapi