Travis CI: Add Java impl build commands.
Travis CI: Add Java impl build commands.

rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang,rgolubtsov/nonlinear-optimization-algorithms-multilang