Metric should be just "gmail_label_unread", using a prometheus label for the gmail label (!)

[lapo-luchini]

As available in this page, I'd like this to become this:

gmail_Label_4301269950433810357_unread 2.0

to become some more like this:

gmail_label_unread{id="Label_4301269950433810357", name="spam"} 2.0

[lapo-luchini]

Trying this on my fork branch "use_labels".

[jamesread]

Hey @lapo-luchini , I totally agree that this is the far more idiomatic way to do this with prometheus. Would you like to PR this? If so, I will accept it.