rename tags to subjects to better match schema
rename tags to subjects to better match schema

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