Complete initialization of the project

[cprudhom]

• [ ] write at least on test per problem
• [x] configure .travis.yml
• [x] update README.md to describe how to use samples

[arnaud-m]

• [x] fix failing tests such as test(org.chocosolver.samples.integer.CostasArraysTest)

[arnaud-m]

Please,

• [x] update to version 4.0.1 (at least a dev branch).

Thanks