Leap examples and adaptor fix

Trying to get the leap motion examples going I ran into 2 problems. This PR fixes them both (at least for me).

+ the adaptor was trying to get the address from `l.Port` instead of `l.Port()`, so there were error messages regarding the attempted use of the formatted memory address for the method (?) as domain and port, e.g.:
```
panic: websocket.Dial ws://0x40810/v3.json: dial tcp: missing port in address 0x40810
```
+ the examples all had callbacks for `"message"` events instead of the capitalized `"Message"` as used in the driver: https://github.com/hybridgroup/gobot/blob/dev/platforms/leap/leap_motion_driver.go#L42

The second issue cased these messages:
```
panic: runtime error: invalid memory address or nil pointer dereference
```

Please let me know if have any feedback. Thanks for gobot! I look forward to playing around more.