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
UTF-8 does not seem to work for characters like ñ on Windows, so use ISO-8859-1 instead

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()