Update author email

[hamogu]

I don't know how long the MIT email is going to continue to work, so seems like a good time to change it to your current institution.

[alexbinks]

I've changed the email in the readme file. MIT --> Tuebingen.

[alexbinks]

Thanks for noticing that my email address needs updating. We can close this one now.

[hamogu]

You could have also accepted this PR, which would have then included both my changes into the main branch of the tesslilator. For two lines of changes either will work, but for more complex changes (which I or other people might suggest in the future) you probably want to go with accepting the PR. Plus, that way the person who wrote that code is associated with that commit through their commit email address. Again, not important for this, but for larger changes, people might want to say in their CV "and I also contributed XXX commits to astropy and YYY commits to tessilator".