Improve package quality

[trinker]

The following tasks need to be done for improving the package quality:

• [ ] Add vignette
• [ ] Add unit test for >= 85% of code
• [ ] Fix all warnings in devtools::document related to missing links
• [ ] Remove deprecated functions

vignette

1. symlinking may be the solution: https://github.com/clarkfitzg/autoparallel/blob/master/README.md
2. Specialized function to copy all/portions of readme? (see: https://github.com/r-lib/usethis/pull/329)

tests

• Open call to anyone who wants an intro to PR in github and knows how to write unit tests