Make cardio git-bisect-friendly

[msiebuhr]

It would be rather nice to execute something like the following:

git bisect start <bad> <good> -- cardio --check "css.countByColor.#eee > 1"

Then it would find the revision between good and bad here the check begins to fail (i.e. the color #eee drops below one).

[papandreou]

Added experimental implementation in 0f271ac. Requires the check parameter to be valid JavaScript, so you need to use bracket notation for things like #eee and class.

cardio example/index.html --check 'html.countByAttributeName.href > 25' ; echo $?

Outputs 0, whereas

cardio example/index.html --check 'html.countByAttributeName.href > 23' ; echo $?

outputs 1 :)