tweak project options
roxygenize with roxygen2 v4.0.2
cosmetic: white spaces
move the default value of initialTileLayerAttribution inside leafletMap() so that the Usage section in Rd will not wider than 90 chars, against which R CMD check will warn
move the doc of leafletMap() and createLeafletMap() from README to roxygen2
move the rest of content in README to a package vignette
roxygenize
import more objects from shiny and htmltools
an alternative implementation of the methods for createLeafletMap() using expression(), so that R CMD check does not complain about undeclared objects like __name__, setView, lat, ...
I think this should be a portable way to store data with non-ASCII characters

read.csv(fileEncoding = 'UTF-8') should convert characters to native encoding on Windows
read.csv() (or the internal scan()) does not work even if we specify the fileEncoding argument, so we have to readLines(), and pass the results to the `text` argument of read.csv()