make .dot graph file from .depend dependency file

  Usage: dep2dot.py [options]
  
  Copyright 2014 drnol (Codeminds, Korea)
  Licensed under the Apache License 2.0
  http://www.apache.org/licenses/LICENSE-2.0
  
  Options:
    --version             show program's version number and exit
    -h, --help            show this help message and exit
    -i FILE, --in=FILE    set input path [default: .depend]
    -o FILE, --out=FILE   set output path [default: dep.dot]
    -s SKIPS, --skips=SKIPS
                          skipping file extensions (*.aaa,*.bbb,...)[default: *.cmx]