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- New class method, `Skeleton.cmd` to create the logger and optparser.
- `Skeleton.run` doesn't set the logger and optparser anymore.
- `Skeleton.write` raises a KeyError exception if a key is missing
instead of prompting the user.
- Removed the `pre_run`, `post_write` and `pre_write` methods. Overwrite
the `write` and `run` instead.
- Added configure_parser() to configure the parser set by `Skeleton.cmd`.
- Add required_skeleton attribute to Skeleton. These skeleton will be run
before the main. They all share the same entries.
- Added verbose options to the Skeleton optparser.
- Added a basic package template extension for `virtualenwrapper.project`.