travis: add IRC notifications

travis: add IRC notifications

This will cause failed builds and when the build flips back to success
to be reported to #xentest on FreeNode. The syntax of the message will
be:
<travis-ci>	xen-project/xen#BUILDID (BRANCH - REVISION : COMMITTER)
<travis-ci>	Change view :
https://github.com/xen-project/xen/compare/RANGE
<travis-ci>	Build details :
https://travis-ci.org/xen-project/xen/builds/BUILDID

The blob was generated with the following command:
travis encrypt -r xen-project/xen 'chat.freenode.net#xentest'

The reason it is encrypted is to prevent people that fork the repo to
spam #xentest. This value will only properly decrypt when running within
the xen-project/xen space.

Signed-off-by: Doug Goldstein <cardoe@cardoe.com>
Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>