Fixed null pointer when no filter is given to list command
Made test more readable
Help shown when no arguments are given on command line
Restored colon in name:version syntax
Merge pull request #13 from mwanji/show_help_by_default

Help shown when no arguments are given on command line
Merge pull request #12 from mwanji/fix_npe_with_unfiltered_list

Fix npe with unfiltered list