Add API for back compat with old package
Skin vignette for web
fixes #20: always quote expr
bump version
Merge pull request #18 from rstudio/feature/legacy

Add API for back compat with old package
Merge pull request #19 from rstudio/feature/website

Skin vignette for web
Make website not self-contained
tweak examples
rename content to popup in addPopups()
add popup to other layer functions
an example of popups for markers
roxygenize
add a GeoJSON example in the vignette to illustrate the popups