(works on my computer).

This allows me to more rapidly develp the Dockerfile. Also this commit
includes a separate conda environment which is going to be used within
singularity

Restructured Dockerfile to utilize layers. Also remove external data (BSgenome.Hsapiens.UCSC.hg38) from image - this has to be provided by the user

Do not install StrandPhaseR! Installation of tools should remain independent of the workflow description