Add support for mybinder.org

[deeplook]

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Adding a "launch binder" button (plus a few additional support files) would let people run these notebooks online using https://mybinder.org on various clouds without having to install anything. This is what I've actually implemented in https://github.com/deeplook/herestapis (including a few more sophisticated APIs like for isolines). Feel free to "steal" from there...

[balotofi]

is this a devrel issue?