seqkit v0.3.4

_64-bit versions are highly recommended._

Changelog

• bugfix: seq wrongly handles only the first one sequence file when multiple files given
• new feature: fxtab can output alphabet letters of a sequence by flag -a (--alphabet)
• new feature: new flag -K (--keep-key) for replace, when replacing
  with key-value file, one can choose keeping the key as value or not.