This will introduce RAPIDJSON_BUILD_THIRDPARTY_GTEST option. If it is set to
TRUE, cmake will look for GTest installation in `thirdparty/gtest` before
looking in other places.
Current default value (OFF) for RAPIDJSON_BUILD_THIRDPARTY_GTEST represents
previous behaviour when system-wide gtest installation is used whenever
possible.
This commit will as well eliminate problem described in #309 when source
directory found is `thirdparty/gtest` while include files are found
system-wide. This however won't give the user possibility to select gtest
installation to use.
* 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`)