pidplots still used old plots syntax, and is apparently mising tests

[mfalt]

Our docs have apparently not been properly compiled (and updated) for a while since they were running the pidplots function which uses the subplot command. Could you update this function @baggepinnen. When this is done, I will make sure to deploy new docs.

[mfalt]

This problem is probably a result of issues #58 and #32