Adjust robot command regex to allow whitespace at end

[gsteinLTU]

Close #171

[dragazo]

We could do this as a normalization step at the start of the function. We might also want to allow multiple spaces by doing something like command = command.trim().replace(/\s+/g, ' '), unless we have meaningful internal spaces somewhere.

[gsteinLTU]

I'd probably agree with just doing a trim first (so it gets whitespace off the beginning too), but I don't think we should "fix" whitespace inside messages. If it was a protocol for actual use I'd be for it, but it'll make the codebreaking activity a lot harder than it needs to be if students are aware.