Add blank requirements.txt for api docs.
Add blank requirements.txt for api docs.

nhzandi/openface,xinfang/face-recognize,francisleunggie/openface,nmabhi/Webface,xinfang/face-recognize,xinfang/face-recognize,nmabhi/Webface,nhzandi/openface,Alexx-G/openface,Alexx-G/openface,Alexx-G/openface,cmusatyalab/openface,Alexx-G/openface,francisleunggie/openface,nhzandi/openface,cmusatyalab/openface,cmusatyalab/openface,nmabhi/Webface,francisleunggie/openface,nmabhi/Webface