add IRC link

Author: DennisOSRM

index.html

@@ -18,7 +18,7 @@
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 <a href="http://map.project-osrm.org/"><img src="images/demo-screenshot.png" alt="Screen Shot"></a>
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-Try our amazing public routing service at <a href="http://map.project-osrm.org/">http://map.project-osrm.org/</a> or follow us on <a href="https://twitter.com/#!/ProjectOSRM">Twitter</a>.
+Try our amazing public routing service at <a href="http://map.project-osrm.org/">http://map.project-osrm.org/</a>, meet us on <a href="irc://irc.oftc.net/osrm">IRC</a> (server: irc.oftc.net, channel: #osrm) or follow us on <a href="https://twitter.com/#!/ProjectOSRM">Twitter</a>.
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 <A NAME="buildstatus"><h2>Current build status:</h2></A>
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