opam: Add build-test section

Signed-off-by: John Else <john.else@citrix.com>
opam: Pull out separate install section

Signed-off-by: John Else <john.else@citrix.com>
opam: Build the docs

Signed-off-by: John Else <john.else@citrix.com>
travis: Use standard skeleton script

Signed-off-by: John Else <john.else@citrix.com>