command to clear the knitr cache for the active presentation
install overlay before common dependencies on the mac
Merge pull request #31 from rstudio/feature/debug-toolbar

add contextual toolbar to the console for debug commands (continue, stop, step)
avoid trying to open directories when checking functions for changes
Merge pull request #32 from rstudio/feature/callstack

avoid trying to open directories when checking functions for changes
tweaks to debug toolbar ui
- style as if it's a primary toolbar
- shorten "Stop Debugging" label
- bump baseline of stop icon up
- add separators between buttons
Merge branch 'master' of github.com:rstudio/rstudio
don't switch to the file being debugged unless the executing line number has changed
make environment pane tolerant to null lists of expanded objects
fix console errors when generating arg list for lapply-ed functions
deal with some pathological object types more gracefully
check for empty source refs before attempting to resolve path
ensure focus and visibility of console prompt where appropriate during debugging
fix problems associated with language objects by moving their value lookups to R
move next button to left side of console debug context toolbar
show <unknown> for language objects that can't be evaluated
hide only the non-user code on the callstack that occurs before user code
Merge branch 'bugs/callstack' into feature/breakpoints
fire event from editor when a breakpoint is set