Remove --install-prefix settings from setup.cfg.
Remove --install-prefix settings from setup.cfg.

 * The default instructions in the README now say to use a virtualenv, and
   these are not compatible with that.

mmaker/bridgedb,mmaker/bridgedb,sysrqb/bridgedb,wfn/bridgedb,wfn/bridgedb,pagea/bridgedb,pagea/bridgedb