Fix for cases where 'repeats' is missing from message_dict

[mcdeck]

I was trying to have home assistant talk to my DHT22 connected via pilight.
However, that failed when trying to read "repeats" from the message_dict.

For some reason it seems that this key is simply not present - not sure why.

Setting veto_repeats to False in the c'tor also seems to work around this problem, but I thought this may be the better solution as other devices may have the key present.

[coveralls]

Coverage remained the same at 100.0% when pulling a52fa6c on mcdeck:master into e111eb5 on DavidLP:master.

[DavidLP]

Interessting, was not aware of this. Thank you very much for your pull request.