Testing VexCL interoperation on Travis-CI

Also make travis badge link to the project page on travis-ci.org
Merge pull request #32 from ddemidov/travis-vexcl

Testing VexCL interoperation on Travis-CI
Merge branch 'master' of https://github.com/libantioch/antioch into unit
Merge branch 'unit' of https://github.com/SylvainPlessis/antioch into unit