New SLAC functionality

Updated new functionality for SingLe-read Analysis of Crosstalks (SLAC)

• This analysis allows the detection of transcriptome-wide crosstalks between pairs of tRNA modifications and modification-aminoacylation.
• Implemented using --crosstalks parameter
• See details of analysis at https://mim-trnaseq.readthedocs.io/en/latest/intro.html and details of outputs at https://mim-trnaseq.readthedocs.io/en/latest/output.html

Bugfixes

• New mods discovery for mitochondrial sequences is now agnostic to coverage at positions in these references. Often, the coverage of mito tRNAs is much lower than their cytosolic counterparts, which makes new mod discovery here difficult when there is a minimum nucleotide coverage filter. This is now disabled.