API: Make version responses work unauthenticated

The / and /v1.1/ URLs should work without requiring keystone auth.  This
patch allows this to happen by adding a WSGI handler to check the path
and direct only the / and /v1.1/ URLs to Pecan without going through
keystone to verify a token.

Change-Id: I22d8d7c91debad7a7959c9d21837dd78c77c9e82