Add information about Snakemake to the development workflow section

[edvinskis]

It would be great to add some of the information that was presented during the coding session to the development workflow section (after merging awe-develop into develop).

[aysunrhn]

Relevant links:

• The Code Refinery documentation: https://coderefinery.github.io/reproducible-research/dependencies/
• The Snakemake github page I prepared to accompany the coding session: https://github.com/aysunrhn/snakemake-tutorial

[aysunrhn]

The snakemake section can be placed under "Development Workflow" in #229