Added docs about -resume.
Added docs about -resume.

chuan-wang/NGI-ChIPseq,chuan-wang/NGI-ChIPseq,chuan-wang/NGI-ChIPseq,ewels/NGI-ChIPseq,ewels/NGI-ChIPseq,ewels/NGI-ChIPseq,chuan-wang/NGI-ChIPseq,ewels/NGI-ChIPseq,ewels/NGI-ChIPseq