Implement more modularity to load adapters from json, instead of changing the .py file

[tamascogustavo]

This is how you can use it:

./Porechop/porechop-runner.py -i fastq_runid_7a4a77339a6966a7f275da1c207d03fd533df80a_0_2.fastq -b testando_novo_pore --barcode_threshold 70 --end_threshold 70  --middle_threshold 95 --min_split_read_size 300 --barcode_diff 2 -t 45 --adapters_file adapters.json