Get customer feedback on logging experience

Currently, the implementation of logging and the description in the README tries to get users to use a single GLOG flag to control output. We agreed to revisit this with user feedback to see if users are confused by this, or if they would prefer some other implementation (e.g., one which uses a single INFO level so that we can use GLOG's INFO/WARNING/ERROR/FATAL levels instead of VLOG) or a description which includes using two different GLOG flags to control output.

Review the logging implementation and README referenced in the issue, then identify how the current single GLOG flag is described and used. Gather user feedback on that experience and document whether the existing approach, a single INFO level, or two GLOG flags should be pursued; done means a recorded direction.

Written by the indexing model from the issue text.