Are you talking about a small group all working together on an IPython notebook + source files? IPython doesn't (yet) support collaborative editing by itself, but SageMathCloud (https://cloud.sagemath.com/, source at https://github.com/sagemath/cloud) has patched IPython to have Google Docs-style collaborative editing. SageMathCloud is still using the latest IPython 2.x release (updated soon, probably in conjunction with upgrading the version of IPython in Sage). Still, it's probably your best bet right now for collaborative editing in IPython notebooks.
That said, several IPython developers are working on adding Google Drive support, and I believe they are working on the collaborative editing capabilities as part of that.