Update bridges

See merge request !18

Update bridges, refactor bridge configuration

See merge request !17

Currently this is the same as the default config, except that Azure
is never used. But it may diverge, so let's make sure it's tested.

The URLs and front domains may change again based on input from the Tor team.

Update bridges

See merge request !16

Update Snowflake params and bridges

See merge request !15

Update bridges

See merge request !14

Ignore redundant calls to start() and stop()

See merge request !13

Don't throw IllegalStateException if start() or stop() is
called in an inappropriate state.

Try to clean up if start() fails so it's not necessary to
call stop() before trying again.

Update README for macOS

See merge request !12