"hisgauge:+10|g" should increase, not overwrite...

[ChristianKniep]

A gauge should be in/decreaseable.
Instantiating somegauge with 5, adding 50 and 500...

# echo "somegauge:+5|g" |nc -u 127.0.0.1 8125
# echo "somegauge:+50|g" |nc -u 127.0.0.1 8125
# echo "somegauge:+500|g" |nc -u 127.0.0.1 8125

...should sum up to 555. But the previous value is overwritten instead.

# whisper-fetch /var/lib/carbon/whisper/stats/somegauge.wsp |grep -v None
1388752330      5.000000
1388752340      50.000000
1388752345      500.000000

Would be awesome if this behavior could be added, I am desperatly looking for a more performant version then the original... :)