Zstandard v0.5.1

• New : Optimal parsing => Very high compression modes, thanks to @inikep
• Changed : Dictionary builder integrated into libzstd and zstd cli
• Changed (!) : zstd cli now uses "multiple input files" as default mode. See zstd -h.
• Fix : high compression modes for big-endian platforms (#123)
• New : zstd cli : -t | --test command