• First implmentation of burning in subtitles. ( --vpp-subburn, #115 )
• New tone-mapping mode added to hdr2sdr of --vpp-colorspace.
  "hable" was the one previously implemented, and "mobius" and "reinhard" is added.
  Please note that usage of hdr2sdr changed, now you need to select from hable, mobius and reinhard, rather than selecting true / false.
• Fix issue that the matrix smpte240m was lacking from --vpp-colorspace. ( #120 )
• Fix issue that the subtitle ID was out of alignment when you pick subtitle to copy by --sub-copy.
• Switch crop implmentation to CUDA when using --avhw. ( #121 )