filter on fragment length

v0.3.6

• allow filtering on fragment length thanks @LudvigOlsen for implementing! (#214)
• fix bug where empty chromosomes are not reported as having 0 depth (#216)

The new optional arguments:

  -l --min-frag-len <min-frag-len>  minimum insert size. reads with a smaller insert size than this are ignored [default: -1]
  -u --max-frag-len <max-frag-len>  maximum insert size. reads with a larger insert size than this are ignored. [default: -1]