Fix the HTTP stack

- The IP drivers now always takes a callback as argument (lib_test/ip needs to be fixed)
- The HTTP drivers do the same thing and always take a callback as argument
Fix the IP tests after the API change in mirage
Add an HTTP test
Fix KV_RO packages for OPAM auto-install
bump to 1.0.2
ignore img files in lib_test
Merge pull request #135 from avsm/samoht-master

Release 1.0.2: HTTP support and OPAM installation fixes
Travis: fix dependencies