[Content Addressable] Install #3: bundler remote resolution and installation

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• bundle install from a remote source resolves and installs the skinny binary.
• No matching skinny binary falls back to fat, then source.

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Depends on local install

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WIP branch - code written but need to tidy up and finish all the tests. Should be enough to give the shape!
master...Shopify:rubygems:ho/bundler-remote-installation-ca