Reduce porechop memory consumption

https://github.com/rrwick/Porechop/issues/77 might be an issue for us. @jennaj is going to check if reducing the total file size helps, if it does we should split the input in a predefined amount of reads to reduce excessive memory consumption.

Start by reading the linked Porechop issue and checking how this repository invokes Porechop. Determine whether reducing the total input file size changes memory consumption; if it does, define and implement the proposed split by a predefined number of reads, then verify that the wrapper processes the split input successfully.

Written by the indexing model from the issue text.