v0.3.0

• chg #16 Improve control flow (bryanp)
• fix #17 Handle IOError from closed selector (bryanp)
• chg #15 Rename default_scheduler_count (bryanp)
• chg #14 Improve cold start of scheduler (bryanp)
• chg #13 Go back to selector-based reactor (bryanp)
• chg #12 Refactor bridges (again) (bryanp)
• dep #11 Change responsibilities of routine sleep behavior to be more clear (bryanp)
• chg #10 Optimize how reactor status is set (bryanp)
• chg #9 Refactor bridges (bryanp)
• chg #8 Cleanup finished routines on next tick (bryanp)