Fixed issue with date offset calculations due to time zone (#284)
Fixed issue with date offset calculations due to time zone (#284)

* - added time zone to date formatter for correct date offset calculations

* - added default parameters to days since function

* - naming change in days since function removing Siren specific naming in an extension for Foundation class

* - added documentation for days since function due to parameter changes in function signature

* - back to old function signature

ArtSabintsev/Siren,ArtSabintsev/Siren