Add README and doc strings & fix bug of commits selection.

* README.rst seems more suiteble than README.md
* commits selection with --range option now includes the end point.
Add working space conservation and restoration.

* work space is restored at the end of running.
* Wherever an exception happend, the work space is restored.
PYTHONPATH bug fixed

* From now on, users don't need to export the PYTHONPATH in their repos.
Fix read basic info
Change logconfig & use 'with' more than file-close
Change --abs to --all
Edit README.

* correct cppflags error