Feature: Check that CircuitPython version on board matches the version configured in piku project

[mraleson]

If the incorrect CircuitPython package is specified in the piku project, then libraries you install may fail with ValueError: incompatible .mpy file.

We could read version from the device instead of setting it in the config file.

Also a good idea to add a note in the README to confirm that the CircuitPython version in the project matches whats installed in the device, and what errors a user might expect if there is a mismatch.

Maybe also add a warning when adding packages if the CircuitPython versions are not matched.