Merge pull request #10 from ropensci/ggplotly

better api and more testing for ggplotly
added slack room line to travis file
pushed a slight change to the knitr hook so that iframes dont have borders
Merge branch 'ggplotly' of github.com:ropensci/plotly into ggplotly
Use ggplotly branch as a 'stage' branch (following Toby's practices).
This conversion for geom_bar() works but is not complete
Small fixes to test
Merge updates