updated ref to docs in README.rst
updated ref to docs in README.rst

peterayeni/rapidsms,ehealthafrica-ci/rapidsms,ehealthafrica-ci/rapidsms,caktus/rapidsms,eHealthAfrica/rapidsms,ehealthafrica-ci/rapidsms,lsgunth/rapidsms,eHealthAfrica/rapidsms,peterayeni/rapidsms,eHealthAfrica/rapidsms,lsgunth/rapidsms,caktus/rapidsms,catalpainternational/rapidsms,peterayeni/rapidsms,caktus/rapidsms,catalpainternational/rapidsms,lsgunth/rapidsms,catalpainternational/rapidsms,peterayeni/rapidsms,catalpainternational/rapidsms,lsgunth/rapidsms