Fix Travis build issues

.travis.yml

@@ -20,7 +20,7 @@ before_install:
        brew install qt5 && \
        brew link qt5 --force && \
        brew install protobuf && \
-       ls -lR /usr/local/include; \
+       ls -lR /usr/local/include/google/protobuf; \
      fi"
 
 addons:

server/device.h

@@ -26,6 +26,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>
 
 #include <QByteArray>
 #include <QHash>
+#include <QString>
 
 class DeviceManager;
 class PacketBuffer;