change overlap function to handle the case insert DNA is shorter than read length
change overlap function to handle the case insert DNA is shorter than read length

In this case some primer/adapter will be read but not trimmed cleanly

OpenGene/AfterQC,haploxer/after,OpenGene/AfterQC,OpenGene/after,haploxer/after,haploxer/after,OpenGene/AfterQC