README fixes
README fixes

Add a dependency, make steps to run clearer, and make
a few miscellaneous markup, phrasing, and layout changes.

dparalen/devstack-gate-test,JohnVillalovos/devstack-gate-test,JohnVillalovos/devstack-gate-test,dparalen/devstack-gate-test,dparalen/devstack-gate-test,JohnVillalovos/devstack-gate-test