v1.15.0

• Add option to create hidden form fields (thanks @jbeuckm!):
  • #730
• Fix bug preventing some forms from being flattened (thanks @btecu!):
  • #722
  • #723
  • #732
• Fix bug causing rotated form fields to be flattened incorrectly (thanks @btecu!):
  • #733
  • #734
• Update logic for updating PDFRadioGroup and PDFCheckBox appearance streams:
  • #743