Refactor server logic into separate file
initial prototyping of subapps
Prevent multiple apps from stomping on server func
Redirect on no trailing slash
Implement Shiny apps embedded as iframes in knitr
knit_print tags and tagLists
More-correct impl of %OR%
Merge remote-tracking branch 'origin/master' into multiple-apps

Conflicts:
	staticdocs/index.r
Restore index.r entries for app obj
Clean up exports, examples
Painful refactoring of server.R

This refactor changes the level of abstraction where sub-apps are implemented.
Sub-apps can basically be thought of as routing (previously called "proxying"
which was way too confusing). A call comes in to /1e8f937a8934/ and it matches
a sub-app path--we need to change the path from /1e8f937a8934/ to / for the
duration of the sub-app's handling of the request.

We used to do routing (nee proxying) at the httpuvCallback level, which added
a lot of complexity because it meant we were compositing HTTP handlers at both
the httpHandler level, and then again at the httpuvCallback level. This
refactor changes it so nobody speaks the language of httpuv except at the very
boundary of Shiny (webserver$createHttpuvApp), everything inside is either an
httpHandler or a wsHandler. So whether you're combining or routing or whatever,
everything now works the same way.
Minor doc updates
Major refactor of runApp/addSubApp pipeline

- shinyUI and shinyServer calls are no longer required in ui.R and server.R
- shinyAppObj renamed to shinyApp
- runApp can take pathname, list(ui=..., server=...), shinyApp, and shinyAppDir
  as appDir argument
- Unify all Shiny app representations around shiny.appobj
- BREAKING CHANGE: shinyUI no longer has a "path" argument
- Instead of returning UI, ui.R can return a function that returns UI; it will
  be invoked each time the page is requested. (Note that this is NOT the same
  as saying ui.R will be run each time the page is requested.) The function can
  take either no args or a single "req" arg which is the request.
Fix scoping bug
Remove obsolete print.shiny.appdir
Allow the use of .Rmd files for shiny impl scripts
Add documentation for handlers/middleware
More docs
Fix Rmd build tooling
Pass R CMD check