we need a BrainLes tutorial for ereg

[neuronflow]

We need a BrainLes Jupyter tutorial for eReg once the API is stable.

The tutorial should..

• be here in a subfolder called eReg
• have a README.md
• show the installation
• show an example of registering/transforming an image using both the CLI tool as well as the Pythonic interface
• show example images to illustrate the registration effects

Have a look at the AURORA tutorial for reference.

[neuronflow]

https://github.com/BrainLesion/tutorials/issues/44