allow user-specified directory structure

[beanumber]

• Maybe have a YAML file with sensible defaults
• Provide an rticles/usethis-style set of templates for certain projects
  • maybe a journal would have their own layout
  • or Project TIER might have their own
  • or a company might have their
  • or an instructor might have their own

[beanumber]

I supposed this would partially relieve us of having to specify where everyone's files have to go. (#9)

We could provide a default "reproducible RStudio data analysis project" template.