Versioning

Now it is easy for developer to apply/remove or push versions.

+ Versions managing tasks for jake
+ Short docs for jake tasks, included them in `README`
+ `CHANGES`, `AUTHORS` and `VERSIONS` files

To get a version information one may use:

    jake version

To apply a new version one may use (creates git tag, uses `VERSION_LOG` to take annotation, affects `VERSION` and `VERSIONS` files, pushes nothing with git, though):

    jake version[v4.2]

To remove some version one may use (to replace `v4.2` with `v4.3`, removes git tag, affects `VERSION` and `VERSIONS` files, pushed nothing with git, though):

    jake rm-version[v4.2:v.4.3]

To push current version to S3, there is a task (affects nothing except S3, uses `.s3` file with credentials):

    jake push-version

To push to `/latest`, use:

    jake push-version[latest]