Add initial CMake support

 * Support for both in-source and out-of-source builds
 * Set library version to 0.12 to map Debian package
 * Add separate options to build tests, examples and documentation
 * Add pkgconfig lookup support (if installed with `make install`)
 * Add CMake lookup support (if isntalled with `make install`)
 * Add Google Test Source lookup
 * Add CTest support for running tests (use `make test` or `ctest -V`)
Fix broken references in documentation
Set separate directory to place binaries
Ignore files generated by CMake
Update readme with changes to CMake build process
Add separate targets for examples and tests
Add namespacetest to the unit tests
Add travis tests to be run from CTest
Try new travis configuration
Lower CMake version to run builds with Travis CI
Add specific target for documentation generation with travis
Fix path to Doxyfile
Modify PATH variable instead of using sudo