Merge pull request #241 from flesire/master

#238 : Upgrade guava to version 15.0
Added license information (MIT)
#237 Using Guava as a cache manager
#237 Integration test
Merge branch 'master' of https://github.com/dcoraboeuf/ontrack
Merge branch 'master' of https://github.com/dcoraboeuf/ontrack