• Fixed const-cast warning by using cast to uintptr_t type
  Thanks to @phillipjohnston for pointing this out and creating a small PR.
• Fixed digit handling for negative float numbers
  Thanks a lot to @vgrudenic for research and creating a fix and new test cases.
• Fixed support for floating NaN
• Fixed warning of comparing floating point with ==
  Thanks to @HarjitSi for bringing this to attention and again to @vgrudenic (see #37)