We maintain time stamps locally.

0.23 was released instead of 0.22.

argparse is available from python2.7, but a lot of python2.7 compilations does
not provide it.

As users expect package to work by default, in case if python used to install
package does not contain argparse, add it to install_requires without requiring
any intervention, because default invocation shall work.

It will allow to minimize common dependency and require ZODB3 module.

This reverts commit d48e4455.