`basilisp.shell.dsl` namespace

[chrisrink10]

I started thinking that Lisps are great for embedding other languages and creating DSLs, so I was thinking it would be great to create a shell script DSL in addition to just a simple shell function or macro in basilisp.shell.

I think something like this would be a great addition to Basilisp's shell namespace, since it's already common to use Python for more advanced scripting when shell scripts won't do. But I found it can be complicated to actually interoperate between subprocess.Popen and standard Python code.