Adopt Tox and Other SunPy packaging tools

[Cadair]

Describe the bug

This is now a sponsored package, so it should be using all the same testing and development tools as all the other sponsored packages. Until I spend the time on the package template, this is still a manual process.

If someone wants to get to this in the next few weeks then great, otherwise I will probably use this as the first test out of the updated package template.

To Reproduce

import sunpy

sunpy.map.Map(...) etc

Screenshots

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System Details

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Installation method

No response

[hayesla]

I guess this is now fixed with #95 right @nabobalis ?

[nabobalis]

Yeah!