Adding target_include_directories directive to auto include headers. This is useful when an external project uses sdsl-lite as a component via add_subdirectory(...) command. Extracted from http://stackoverflow.com/a/18697099 .
Adding minumum CMake version 2.8.11 (required for target_include_directories). More info at http://www.cmake.org/cmake/help/v2.8.11/cmake.html#command:target_include_directories .
Merge pull request #209 from diegocaro/master

Adding target_include_directories directive to auto include headers