compile-file doesn't work if run noninteractively

[sjl]

I'm trying to run wisp -c foo.wisp from make, but the cond here says that if we're running non-interactively we should always compile from stdin (and so it just ignores my -c foo.wisp and compiles the (empty) stdin into void 0):

https://github.com/Gozala/wisp/blob/master/src/wisp.wisp#L97-L102

It would be nice to reorder this so the check for -c comes first.