Removed Travis CI config.
Merge pull request #586 from LaurentGomila/feature/no_travis

Removed Travis CI config.
Fix build of the SFML target on OS X with Xcode
Removed vertical tab support from Text (#442).
Merge pull request #596 from Ceylo/bugfix/595_OSXFrameworkCreation

#595 Fix build of the SFML target on OS X with Xcode

Nevertheless, Xcode generator is not officially supported by SFML
Updated glext, removed glxext.

Removed glxext in favor of the system version.
Add CMake config file to replace the FindSFML module