Clarify text in heat/tests/templates/README
Clarify text in heat/tests/templates/README

Fixing punctuation and re-wording to make the meaning of some sentences
more clear.

Change-Id: I3fad879e4d3c60bc0a04bc67d86d4d9866bbdaaf

dims/heat,steveb/heat,maestro-hybrid-cloud/heat,gonzolino/heat,pshchelo/heat,gonzolino/heat,dragorosson/heat,redhat-openstack/heat,jasondunsmore/heat,rickerc/heat_audit,pratikmallya/heat,openstack/heat,cryptickp/heat,cwolferh/heat-scratch,openstack/heat,rh-s/heat,citrix-openstack-build/heat,noironetworks/heat,rh-s/heat,JioCloud/heat,pratikmallya/heat,rdo-management/heat,NeCTAR-RC/heat,rickerc/heat_audit,cryptickp/heat,varunarya10/heat,miguelgrinberg/heat,cwolferh/heat-scratch,dims/heat,srznew/heat,pshchelo/heat,steveb/heat,srznew/heat,takeshineshiro/heat,JioCloud/heat,ntt-sic/heat,miguelgrinberg/heat,ntt-sic/heat,citrix-openstack-build/heat,maestro-hybrid-cloud/heat,jasondunsmore/heat,redhat-openstack/heat,noironetworks/heat,dragorosson/heat,varunarya10/heat,NeCTAR-RC/heat,takeshineshiro/heat,rdo-management/heat