make arakoon compile with ocaml 4.02 (for now with unsafe_string compiler flag)
update CI env to use ocaml 4.02
bump to lwt.2.4.5
install quickcheck dependency
update travis to ocaml 4.02
fix plugin example for the changed user functions/hooks in 1.8
Merge branch '4.02' into 4.02-1.8

Conflicts:
	src/node/simple_store.ml
Merge pull request #519 from Incubaid/4.02-1.8

4.02 1.8