Paper: Gammapy: Gamma-ray astronomy with Python (C. Deil)

Can this contribution still be considered if we have it finished by tomorrow?
I'll make the Gammapy 0.1 release tomorrow and would very much like to have a EuroScipy 2014 proceeding about it.

In any case, apologies for the late submission!
There is a [scikit-image paper](https://peerj.com/articles/453/), and you can find references in it for other libraries here (e.g. SciPy and Matplotlib).