Feature Request: get an arbitrary sensor from the command line

[marksherman]

I'd like to use iStats to get the value of one of the extra sensors as part of another script, but you can only get a single-line response if you ask it for istats cpu, which is hard-coded.

I'd like to be able to do something like istats TC0E or istats --key=TC0E to return ONLY that sensor.

[marksherman]

This feature could satisfy #36 by allowing shell aliases to effectively set your personal cpu sensor, or any other customization that the user wants.