add run_document command; collect rmd_warning metadata
Merge remote-tracking branch 'origin/master' into feature/shiny-docs

Conflicts:
	R/render.R
load shiny library during render
support reactive documents
optionally auto-refresh the document when it changes
remove Shiny reactive adapters (moving to Shiny)
Merge remote-tracking branch 'origin/master' into feature/shiny-docs
document runtime parameter; clean up shiny dependency
rename run_document to run
Merge pull request #48 from rstudio/feature/shiny-docs

Add support for running Shiny documents