Hash serial_number

From now on, do not send plain serial number, but
the hashed version.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Add retry restrictions

Restrict harvest client so it won't retry too many times
in a short period of time when it fails to send data.

IE, while connecting to ad-hoc network.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Increase selection probability

In practise (1/7) was too low, and for our testing
period we need more (1/3) feedback.

We can always change it back, if needed.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Include mime_type metadata

mine_type was the only metadata we were not collecting,
it can be useful to make deeper insight about some
activities that support multiple file types.

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>
Release 0.2.0-1

Signed-off-by: Martin Abente Lahaye <tch@sugarlabs.org>