CBT libraries for Ruby

• minitar is pure Ruby: no native library, works everywhere. Reads and writes POSIX tar.
• ffi-libarchive binds libarchive, which accepts every tar variant and also reads ZIP, RAR and 7z. Needs the libarchive shared library.

• ffi-libarchive Read and write CBT (TAR) comic book archives in Ruby with ffi-libarchive, a libarchive binding: pages in natural order, cover, ComicInfo.xml and creating a CBT.
• minitar Read and write CBT (TAR) comic book archives in pure Ruby with minitar: list pages in natural order, extract the cover, read ComicInfo.xml.