Minor compatibility breaks
* Update `git_clone_or_pull` to full clone by default
Features
* Add module `network.url`
* Add mixin `django.forms.mixins.CreatedByMixin`
* Add mixin `django.forms.mixins.StaffOnlyFieldsMixin`
Fixes and enhancements
* Add/fix docstrings and unit-tests
* Use `xrange` and `iter{items,keys,values}` under Python 2
* Replace `nose.tools` by `pytoolbox.unittest.asserts`
* Make `RequestMixin` more transparent
* `network.http.download_ext`: Pass `kwargs` to `iter_download_to_file`
* `django.views.mixins.AddRequestToFormKwargsMixin`: Check form "handles" request as `kwarg` based on its class