[travis] add .travis.yml file
[travis] add yarp installation options from documentation
[travis] correct build command and install opencv 2.4

OpenCV 2.3 has a bug with clang related bug http://code.opencv.org/issues/1432 .
[travis] add confirmatuion flag for install opencv 2.4
[travis] add travis badge to readme
[travis] add os x support
[travis] allow failure on osx
[travis] added missing then
[travis] remove badge from readme to avoid confusion with dashboard results
[travis] use the same compilation option of the dashboard
Merge pull request #37 from traversaro/patch-1

Initial travis support for icub-main;
travis support for icub-main enabled