add leaflet-measure control

[timelyportfolio]

leaflet-measure seemed like a very good and easy addition to leaflet. It adds a control to measure a polygon that a user can draw onto a leaflet map. I tried to model the pull on others that I have seen recently. Please let me know if there are any consistencies.

Here is an example with screenshot.

library(leaflet)

leaf <- leaflet() %>%
  addTiles() %>%
  # central park
  fitBounds(-73.9, 40.75, -73.95,40.8) %>%
  addMeasure()

leaf

# to remove the measure
leaf %>% removeMeasure()

[jcheng5]

No need for layerId parameter

[jcheng5]

Other than the comments I made this looks great, thank you!

[timelyportfolio]

@jcheng5, very good suggestions. Thanks for the review. I think all changes have been made.

[jcheng5]

Great! Last thing we need from you is a signed CLA, if you don't mind. https://www.rstudio.com/wp-content/uploads/2014/06/RStudioIndividualContributorAgreement.pdf If scanning isn't convenient, you can just email a cellphone pic of the signed agreement to [email protected].

The CLA assigns copyright to us so we can relicense our package in the future if necessary, e.g. to a different version of the GPL or to a more liberal BSD/MIT style license. (Without having CLAs on file for all contributors, we'd have to try to wrangle a unanimous vote to make these kinds of changes.)

[jcheng5]

I received the CLA, thank you.