poliastro does not work on Binder

[astrojuanlu]

🐞 Problem

At the moment poliastro can't be deployed on Binder.

To reproduce, try it.

💡 Possible solutions

It has been suggested that there's a problem in our Dockerfile. We should either:

• Fix it
• Find an alternative method that works

I was never fond of Docker for library code, so if we can do without it, 👍

📋 Steps to solve the problem

• Comment below about what you've started working on.
• Add, commit, push your changes
• Submit a pull request and add this in comments - Addresses #<put issue number here>
• Ask for a review in comments section of pull request
• Celebrate your contribution to this project 🎉

[iamabhishek0]

@astrojuanlu I have fixed the Dockerfile, I suggest having a requirements.txt. If ever there's a need for a Dockerfile it can be used, I have tested it on Binder.

[astrojuanlu]

Sorry @iamabhishek0, too late - I removed it. Too much complexity for what should be a simple problem. Now we are using a requirements.txt, as advised :)