Cekit

Modules required by other modules are now resolved properly (162)

* Added back possibility to inject local modules for compatibility reasons 148

* fixed Descriptor objects merging 144

* Fixed OSBS builder to build image which doesn't have any artifacts defined (140)

* Added support for module versioning - http://concreate.readthedocs.io/en/latest/descriptor.html#module-installation
* Added proper overrides documentation
* Fixed overrides support for modules (92)
* Improved OSBS shell session - Concreate now prefix PS1 variable to show you are in a Concreate session (84 )
* Fixed fetching URL resources, if url is specified and cacher is missed, it will try original url (77)
* Fixed default values handling for run and execute
* Deprecated --build-tag option, you should use --tag instead
* Fixed possibility to have duplicity environment variables in generated Dockerfile (119)
* Fixed rhpkg new-sources causing git to ignore some file changes (123)

* Exit with proper exit code when tests fail to execute
* Updated path to repository with steps