Logging directory hardcoded in logging.cpp

[abedegno]

The examples have a hardcoded logging directory in logging.cpp
/Users/adamfowler/Documents/marklogic/git/mlcplusplus/logs

This causes errors when running the precompiled errors. It would be best to leave these blank as GLOG defaults to /tmp and give users the option to override them using gflags.

[abedegno]

The hardcoded log directory appears to be ./logs - creating such a directory allows the samples to run.