correct binder link

README.md

 # Deep dive into solving the scattering problem with Kwant
 Slide deck for a coding journal club I gave at the Quantum Tinkerer group (TU Delft) in September 2019.
 
-[![Binder](https://mybinder.org/badge_logo.svg)](https://mybinder.org/v2/gh/jbweston/kwant-scattering-problem-journal-club/master)
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