CMakeLists : put the Gtest related stuff into a separate file.
Add the Easylogging++ header file to the CMake build process.
Add an example of how to use the logging library.

See the complete documentation at
https://github.com/easylogging/easyloggingpp.
Add basic logger setup.

Change the initialize_logger methods in src/client/logging.cc and
src/server/logging.cc to chage the logging parameters.
Merge pull request #10 from Neki/topic/bf_add_logger

Add a logger with a basic configuration. Closes #5.