v0.6 Release

- Major update: Changed all port access from SBI/CBI to OUT. This
removes
a timing inconsistency between reduced core AVR and standard AVR,
avoiding separate
implementations for different cores. A disadvantage is increase register
usage.
- Added a "ws2813_sendarray_mask" function which allows to pass a
bitmask for the
selected port. This allows controlling up to 8 independent LED strips.
- Removed functions for interrupt handling. Avoiding interference with
interrupts
is now up to the user.
Merge branch 'master' of https://github.com/cpldcpu/light_ws2812