Revert to devtools:::install_version. Refs #19.

Implementing parts of the original `bundle` functionality with calls to
devtools `install_version` and `install` functions.

Note that the build is not passing. I can run all tests using
`testthat:::test(fresh=TRUE)`, but `devtools:::check()` does not pass, nor
does `R CMD check`. Committing this in order to save my
work-in-progress.