CRAN version

fix

• use 1/4 line for typical offest (as it is done in mapsf)
• better management of symbol sizes (leg = "symb")
• better management of boxes offest (leg = "typo")

feat

• added a NEWS.md file to track changes to the package.
• add a link to igraph example (#2)
• add a GIS-like example (#1)
• add alpha transparency for palettes (#4)