Issue #51: make sure API key is lowercase.
Issue #52: set Peewee and Requests log level to CRITICAL if app log level isn't DEBUG.
Removed unused import.
Removed note about untested PostgreSQL support.
remove transaction around OPML import

This removes indentation, but no code changed.

The transaction isn't necessary; aborting an import will not lead to inconsistent data.
enable autorollback for postgres

This fixes #54 but pretty much prevents us from using explicit transactions.