Add depexts for a XenServer environment/OS

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #34 from djs55/add-xenserver

Add depexts for a XenServer environment/OS
Rename XenServer to centos

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #35 from djs55/add-xenserver

Rename XenServer to centos
xapi depends on new rrdd-plugin and xenctrl

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
rrdd-plugin depends on rrd-transport

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
travis: work around opam ocamlfind problem

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
travis: try again to work around opam ocamlfind problem

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
travis: oh why do you dislike me so?

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
travis: travis travis

Signed-off-by: David Scott <dave.scott@eu.citrix.com>
Merge pull request #36 from djs55/new-packages

xapi depends on new rrdd-plugin and xenctrl