add note about mailing list change
Floodlight OpenFlow Controller (OSS)
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-Build Status:
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+Attention!
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+
+As of August 2018, the Floodlight mailing list has moved! Please see **Documentation and Support** below for up-to-date support information.
+
+Build Status
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[![Build Status](https://travis-ci.org/floodlight/floodlight.svg?branch=master)](https://travis-ci.org/floodlight/floodlight)
