add a requirements file for RTD. thanks to @bchapman
add a requirements file for RTD. thanks to @bchapman

brentp/gemini,arq5x/gemini,bpow/gemini,arq5x/gemini,bgruening/gemini,xuzetan/gemini,udp3f/gemini,arq5x/gemini,xuzetan/gemini,bgruening/gemini,udp3f/gemini,udp3f/gemini,brentp/gemini,udp3f/gemini,xuzetan/gemini,bpow/gemini,bgruening/gemini,xuzetan/gemini,brentp/gemini,arq5x/gemini,bgruening/gemini,brentp/gemini,bpow/gemini,bpow/gemini