New-style pylint pragmas
More linting!
Handle clauses in streamer more clearly

There was some code here that was a little confusing.

- Flip order of some `if not condition ... else` clauses to avoid the
  need for readers to parse the inversion
- Reduce redundant code where lists were handled
- Be more cautious about key lookups for 'case_sensitive' by defaulting
  to `True`.