Slightly simplify round-trip-validation-error
Correct hesokuri.see/shrink documentation
Implement dynamic-config module for managing the configuration file

This is part of an effort to support automatic discovery of repositories (See
https://github.com/google/hesokuri/issues/8). This module renders the
updateable-heso module obsolete. It takes a config file, and monitors it for
changes, invoking a callback when necessary. In the future, this module can
handle automatic updating of the config file.