Trailing slash is mandatory for argv[1]

Omitting the trailing slash while giving the path to uav objects xml definitions yields an error

```
./bridge uavobjectsdefinition
2015/06/21 14:47:39 open uavobjectdefinitionacceldesired.xml: no such file or directory
```

```
./bridge uavobjectsdefinition/
2015/06/21 14:47:50 Websocket server started
```
