fix the regression issue of clustering reversed UMI

optimize createCluster

fix the bug in main

improve the speed by skipping large low complexity cluster

which is usually caused by mapping errors

set version to v0.7.0

ignore ref bases other than A/T/C/G

set version to v0.5.0

set version to v0.4.0

small revision for the quit_after_contig option

write unmapped reads directly