white (or optional other) background color for printed html pages
Add "attachment" parameter to htmlDependency
HTML escape background
Merge remote-tracking branch 'origin/feature/html-background'

Conflicts:
	R/html_print.R
	man/html_print.Rd
add background parameter to save_html
Merge pull request #15 from rstudio/feature/dependency-attachment

Add "attachment" parameter to htmlDependency
Suppress R CMD check warning about unused import
Revert "Suppress R CMD check warning about unused import"

This reverts commit f21e08ff9d5fb39d89b6b06d5777a687eded1576.
Safer squelching of utils import warning
Merge branch 'master' of https://github.com/rstudio/htmltools