message-switch: use ./configure.ml; remove stale dep on xenstore

Signed-off-by: David Scott <dave.scott@citrix.com>
travis: this is an overlay opam repo

Signed-off-by: David Scott <dave.scott@citrix.com>
travis: remove installability test; insist package must be installable

Signed-off-by: David Scott <dave.scott@citrix.com>
travis: we're using the old repo metadata layout

Signed-off-by: David Scott <dave.scott@citrix.com>
message-switch: make the configure program first, then run it

Signed-off-by: David Scott <dave.scott@citrix.com>
Merge pull request #18 from djs55/message-switch.0.10.3

message-switch: use ./configure.ml; remove stale dep on xenstore