updated documentation: roclet names, seealso

... because I often find myself looking up the arguments to roclets, the goal is for `c("collate", "namespace", "rd")` to show up automatically when I type `'document(' -> Tab` in Rstudio.

While here, I also added references to roxygen2 in function description and @seealso
Updated test() doc for updated testthat structure
Fix typo in add_desc_package
Merge pull request #505 from kevinushey/master

Fix typo in add_desc_package
Don't use --as-cran
Fix docs for add_rstudio_project
Rename add_travis to use_travis
Merge pull request #499 from imanuelcostigan/fix_test_doc

Updated test() doc for updated testthat structure
Document use_travis
Return path in loaded_packages. Closes #486
Merge pull request #485 from dlebauer/patch-4

updated documentation: roclet names, seealso
Improve document documentation
Bump roxygen2 requirement to 4.0.0
Import rstudio api.
Closes #458
No deps for new package
Add arbitrary pre-release questions
Only show news if present
Rename cran notes
use GitHub API to download archive in install_github

- always use package name for naming downloaded file in install_github

- include tests

- bump httr dependency; don't explicitly set user agent
    - also affects one other GET call
Use new CRAN submission process.
Closes #430