Usability improvements

SpikeDetekt now:

* Gives a descriptive message when KlustaKwik doesn't return properly
* Handles --overwrite in a more sensible way
* Boundary checks some KlustaKwik parameters before passing them on (MaskStarts / MaxPossibleClusters / Max/MinClusters)
* Prints version on run
* Has more descriptive error messages
* Bumped version to 0.3.0.rc2
`.rc2`?