Improved FLASH_Update() method - make OTA Update more reliable
FLASH_Update-Erase Flash pages for failure and return next_chunk_index
Important - Assigned RTC Alarm higher priority than RTC Seconds interrupt
Enter Standby Mode at startup if flag is set and enable RTC interrupts
Merge pull request #20 from spark/feature/sleep-mode-update

Feature/sleep mode update
Merge pull request #19 from spark/bug-fixes

Improved FLASH_Update() method - make OTA Update more reliable
Enable factory reset from software

Requires bootloader change to actually be used
Merge pull request #21 from spark/feature/software-factory-reset

Enable factory reset from software
Merge tag 'spark_4' into compile-staging

Tag version 0.2.1 as spark_4