Update outdated description for download command

Update the description of the configure command to display the correct alias -d for the --download-path option. This was forgotten when the alias changed from -l to -d in commit 15016c79ad017a92a5c08fededa5854471026ded.

(I would also vote for using the more explicit --email --password and --download-path options in the description but did not include them in the PR.)
Merge pull request #27 from sebroeder/patch-2

Update outdated description for download command