* Renamed check_files to brd.
* Started updating README.
* Cleaning up command-line help.
* Changed output file option for dupe_files and dupe_trees to use -o instead of positional argument.
* Added output file option to diff mode similar to dupe_files/dupe_trees.
* More tweaking of online help.
* Changed default database name to sys.argv[0] + '.db'.
* More updates to online help.
* Finished command-line help.
* Finished README.