[CMake] Generate cmake target that other libraries can use (#86)

Generates cmake target that other libraries can use to express
their dependency on this library and retrieve any configuration
information such as the include directory.

test/test_cmake/main.cpp

@@ -0,0 +1,7 @@
+// Dummy executable, just to make sure
+// that we can find the Boost.predef header files
+#include <boost/predef.h>
+
+int main() {
+
+}