mirage-www: depend on latest cow due to interface change
Travis: flesh out the PPA/OPAM matrix
travis: skip depexts on opam 1.0.0 as the semantics changed
mark uri as ocaml 4+ only (due to compiler-libs detection failure)
correct mirage-www cow constraint
cohttp: sync minimum uri version to >=1.3.8
mirari: depend on ipaddr
cohttp: further uri constraint fixes
+uri.1.3.10 (should work with 3.12.1 now)
tweak older mirage-www constraints to help it build
mirari: constraint to ocaml 4+ due to various problems in the runtime code (some as simple as missing String.trim)
mirage-www: require mirari 0.9.7+
travis: echo OCaml and OPAM versions to aid debugging
+uri.1.3.9
Merge pull request #1146 from mirage/master

travis: test full matrix of opam/ocaml versions