Add JSON output file with contamination results option

[JuPrgn]

Relates to #4

Add json option -j to save contamination results in [output name]_contamination_results.json (only with terminal option active)

Command : python AuthentiCT deam2cont -t -j -o out.txt -s 10000 test_dataset\Sima.incisor.subset_test.sam

Generates following files :

out.txt

#contamination_rate	#nodeam	#deam5	#deam3	#deam53
0.8671328671328671	174	6	5	13

out_contamination_results.json

{"contamination_rate": 0.8671328671328671, "nodeam": 174, "deam5": 6, "deam3": 5, "deam53": 13}

[apeltzer]

Looks like a MultiQC module might be available soon ;-)