Fixes#28

```
prem@prem-Vostro-2420:~/Code/czmqpp-master/examples$ g++ -std=c++11 ironhouse2.cpp -o ironhouse2 -lczmq++ -lczmq -lzmq -lpthread
prem@prem-Vostro-2420:~/Code/czmqpp-master/examples$ ./ironhouse2 
ZAUTH I: PASSED (whitelist) address=127.0.0.1
ZAUTH I: ALLOWED (CURVE) client_key=m<*t@Gy-4P[iHbPVeuhax]T8Eo$fLJe5Mls0PmSU
Ironhouse test OK
prem@prem-Vostro-2420:~/Code/czmqpp-master/examples$
```