download
download(my, url, to_dir=".", filename='', md5_checksum="")
Download a file from a given url
param:
url - the url source location of the file
keyparam:
to_dir - the directory to download to
filename - the filename to download to, defaults to original filename
md5_checksum - an md5 checksum to match the file against
return:
string - path of the file donwloaded