v0.0.31

Major changes:
Spike-in adaptation
- supports multiple genome mappings
- detects Spike-in in sample sheet and maps to the genome
- creates a dict of genome indices
- main output structure changed to Mapped/[Main|Spike-in]

Minor changes:
Support for ATAC in ChiPQC report:
- Per position calculation of library complexity
- Duplication rate + Library complexity plots
dry-run performance boost
- addresses #115