After you installed all the depencies, install the CRefEx python module as usually by typing:
python setup.py install
CRefEx relies on the following external modules/libraries:
CRF++: a C++ implementation of CRF written by Taku Kudo (I’m using version 0.53) which provides a python bridge.
For the installation of the python module to call CRF++ please refer to the instruction in the ./python/README file (the path is relative to CRF++’s installation folder)