Add CMake configuration

The portable build configuration is convenient to build and run examples.
Ignore CMake build subdirectory
Ignore files generated for IDE support
Improve compiler flags setting
GCC 4.3+ is recommended

Apparently, support for the right angle brackets (N1757) is required, which is available in GCC 4.3 or later.
Merge pull request #6 from mloskot/cmake-build

Add CMake configuration