minor refactorings; doc; Notification references;

Among minor refactorings and documentation, added references
between Notification interfaces.  This will allow a developer to trace
a Notification back to a specific repository (among other things).
fixes (anomaly) KeyNotFoundException thrown in RemoteInfo ctor;

'git remote show {remote}' seemed to have an anomaly in the output.
See http://stackoverflow.com/q/15125151/495132 for more info.

Fixes #24.