CMake 2.8.5 or higher is required

make with error for the lower version:

Linking CXX executable ../../bin/jsoncpp_test
/bin/sh: $<TARGET_FILE:jsoncpp_test>: command not found
make[2]: *** [bin/jsoncpp_test] Error 127
make[1]: *** [src/test_lib_json/CMakeFiles/jsoncpp_test.dir/all] Error 2
make: *** [all] Error 2

due to 
http://stackoverflow.com/questions/5410164/how-do-i-use-a-targets-path-in-add-custom-command-in-cmake#comment6139682_5410794
Merge pull request #50 from sergzub/master

 CMake 2.8.5 or higher is required