Added version string support to optparse interface config files

optparse interface config files are now required to have ```__version__``` defined so that optparse will report the right version string when called with ```--version```.

In practice, this shouldn't make the config files any more complex than they were already since ```pyqi make-optparse``` requires that the user provide a version string, and it fills in that value in the header automatically.

The docs have been updated to make note of this. Tested that this works with all pyqi and biom commands.

Fixes #139.