Added env picker, rate timezone picker

Viewer now supports Passport's sandbox environment in addition to production; also added a toggle to make it easier to look up rates in local time (local to the parking zone).

UI improvements and networking fixes

Minor UI tweaks, now using published passport-parking library.

Made client secret fields into a password field for privacy.

Bug fixes, minor style adjustments

Resolved a bug that affected the user's ability to provide client ID and secret.

Initial release

Initial launch of the rate viewer based on Passport's parking APIs: https://developer.passportinc.com.