v0.5.4

Changes

• Extended Unsafe API with a function allowing to iterate over all Buffer's segments #383
• Implemented ByteString conversion to/from NSData on Apple platforms #384
• Implemented extensions to read/write ByteString from to/from ByteBuffer, as well as representing
  ByteString as a read-only ByteBuffer on JVM #387
• Implemented ByteString factory accepting unsigned bytes #390
• Reimplemented various functions using Unsafe API #337
• Minor documentation improvements

Thanks to @qwwdfsad, @JakeWharton, and @joffrey-bion for contributions!