Start adding an Environment object and a loader
Refactor create command to use Environment object
Add to_yaml() to Environment
add in support for passing a stream
Ensure actual YAML output is always generated and make test more robust
Remove mock testing
Switch over to using env.to_yaml()
Refactor to preserve order when exporting
Remove this special import
Bump to next dev version
Remove unused code
Fix import
Remove unused imports
Remove more unused imports
Add add_package() to allow modifying an existing package's dependencies
Add a load_from_directory() function to get an Environment object
Ensure that the filename property is preserved
Ensure that returned to_yaml() is always in yaml style
Add in save() functionality
Remove the raw dependency/dependency stuff in favor of a real object

Keep track of two sets of dependencies seemed silly.  This simplifies
the code by only have on real Dependencies object that we can add
functionality to and test independently.