Hardcoded python2.7 in Makefile

[mtngld]

PYTHON_LIBRARIES is hardcoded python2.7
https://github.com/BVLC/caffe/blob/master/Makefile#L194

I am using a system that does not have python2.7 and In addition to changing PYTHON_LIB value in the Makefile.config I also had to change that line to PYTHON_LIBRARIES := boost_python python3.4m in order to succefully compile pycaffe.

I am not sure if the solution is to expose PYTHON_LIBRARIES to Makefile.config or to create a more intelligent logic inside Makefile to figure out the python library version.

[untom]

I just ran into this issue myself, it would be nice if this could be fixed.

[lukeyeager]

Try using CMake. The TravisCI build uses CMake when testing python3.

I think we should get rid of the manual Make build entirely (#3351).