`dppvalidator schema download` returns version info

[absoludity]

I was testing whether I can download other schemas to validate against, but found I couldn't get a result from the download subcommand even with the default argument values.

Steps to reproduce:

1. dppvalidator schema download

Expected result:
0.6.1 schema present in the current directory

Actual result:
The dppvalidator version information is the only output on the console:

$ dppvalidator schema download
dppvalidator 0.3.2

which is identical to:

$ dppvalidator --version
dppvalidator 0.3.2

Excellent tool otherwise though!