Clean up code and make it more robust

  - prevent packing fonts as symlinks (bug?)
  - use temporary directory to make package
  - deal with unusual characters in filename of font
  - delegate hash calculation to updpkgsums
  - handle errors better
Add -S as alias for --source since that's what makepkg uses
Change version and description

  - set version to 1.0.0 instead of 1.0
  - set description to "Custom font" instead of "{fontname} custom font"
Add flags for name, version, release number, and description
Add support for multiple files