1.2.3 fixes

- updated podspec
- added open / close basement methods (thx
https://github.com/bomjkolyadun)
- prepareForReuse fix (thx https://github.com/bomjkolyadun)
- fixed warnings for arm64
- demo app shows the basement on startup to hint the user (thx
https://github.com/bomjkolyadun)
- updated README