Revert "check for upstart before using initctl"

This reverts commit 57b8b9a.

The original commit was made for compatibility with Docker, which has
/etc/init/ but not a working implementation of upstart. However, it was
since discovered (by @aronatkins) that not all CentOS configurations
have /usr/share/upstart/, so we need a better approach to determining
whether there is a functional upstart.

Merge pull request rstudio#910 from rstudio/feature/js-css-notebook

Add support for JavaScript and CSS chunks in R notebooks

Merge pull request rstudio#907 from rstudio/feature/cran-rmarkdown-rs…

…connect

Install rmarkdown and rsconnect from CRAN

Merge pull request rstudio#907 from rstudio/feature/cran-rmarkdown-rs…

…connect

Install rmarkdown and rsconnect from CRAN

Merge pull request rstudio#903 from rstudio/feature/terminal

fix Win32 build break (missing comma)

fix issues related to chunk insertion from editor toolbar

use [[ to read yaml front matter for custom knit function

Revert "detect objects containing active bindings"

This reverts commit 4094fc2.

Merge pull request rstudio#898 from rstudio/bugfix/notebook-cross-device

Fix notebook errors on some mounted filesystems

update NEWS