WARNING: require recent slapos.core.

Allows not to always hack around to have dev version.

This recipe was colliding with slapos.recipe.template
recipe.

Moreover, this is useless since slapos.recipe.template provide
the same functionality.
(cherry picked from commit 4195f78b because of ugly merge.)

Conflicts:
	setup.py

Previous URL was not available. Replace it with available URL. It is probably better to host this file by ourselves. Otherwise this link will be broken again in near future.

It allows to develop and test the egg inside of the slapos instance.

This reverts commit 509d47a6.