Speech transcription fails with records of more than ~8 seconds

[davidfoerster]

When sending speech records longer than roughly 8 seconds to Google's speech-to-text web service, it returns an error. No cut-off to a suitable length is performed.

Kaleidoscope should work around this limitation and cut off the recording after a suitable interval.

A preliminary implementation of such a feature is available in b508abd (branch feature/restrict-speech-record-duration) and requires further testing before merging into master.