Create ResponseAnalyzer and TranscriptionFileService from helpers

[KatieProchilo]

Rebased and ready to merge.

The now-deleted helpers.ts has been split into two classes/files: ResponseAnalyzer and TranscriptionFileService. Each of these classes is invoked exactly once, with the exception of invocations in test files.

• ResponseAnalyzer handles responses, including actual transcriptions, from the STT service. It will analyze, return, and/or print data based on the responses.
• TranscriptionFileService contains helpers for reading, writing to, and parsing transcriptions.txt, or whatever the passed in transcription file is called.

Reused variables are now fields if possible, though I'm sure there's room to improve even more in this area.

Some other cleanup was done, including:

• Using arrow functions whenever possible.
• Every function has a return type.
• Import modules first, then local files.
  • Imports are alphabetized within their group.
• Function signatures and imports kept at <= 80 characters.
  • I'll create an issue so that we can programmatically enforce this later on - this will probably be done with Prettier.

[Joll59]

@KatieProchilo Merge after reading comments.