This RFC is to add the display_firefly backend for afw.display to lsst_distrib. This change will bring along the firefly_client and ws4py dependencies which were added to the stack in RFC-248.

The display_firefly backend can be used with the server at http://lsst-demo.ncsa.illinois.edu/firefly, the server at http://irsa.ipac.caltech.edu/irsaviewer, or with a server deployed with Docker or by other means. Documentation for display_firefly is available (for the time being) at display-firefly.lsst.io and docs for firefly_client at firefly-client.lsst.io

Minimal automated tests have been added to display_firefly and firefly_client packages. All packages build on Jenkins. The main test mechanism for afw.display backends is running afw/tests/test_display.py interactively.