API cleanup (breaking)

[cleishm]

It would be an API breaking change, but I'd also strongly encourage:

• Moving RE_DEFAULT_PIN, RE_DEFAULT_STEPS, and RE_LOOP_INTERVAL to class static constants (rather than global).
• Moving EncoderType to a class scope enum (rather than global).
• Moving RotaryEncoder::loop() into private scope.

Originally posted by @cleishm in #18 (comment)

[MaffooClock]

That sounds like a solid move.

I can tag and publish the changes you've contributed thus far into v1.2.0, so existing projects can freeze at v1.x. Then merge breaking changes you suggest, along with appropriate README updates, and tag/publish as v2.0.0.