started on logfile class, wrote constructor

- makes <code>log_directory</code> (default name: "log") if it does not exist
- log files named using the convention:
>   splatfilch_YYMMDD_HHMMSS.txt
  so they should sort automatically using name or date
- writes title to beginning of log file

- no other methods for class written yet
basic logfile class done

- better verbosity levels
- docstrings
- default verbosity = none (quiet)
- keeps file open during run, flushes/closes on delete
- error(msg) always prints (in quiet, verbose, or debug mode)
- warning(msg) prints in verbose or debug modes
- info(msg) prints only in debug mode