change: add leading zeros to travis build number up to 4 chars
change: add leading zeros to travis build number up to 4 chars

This allows all past and future tags to remain ordered while listing
them with 'git tag', up to build 9999.

basimilch/basimilch-app,basimilch/basimilch-app,basimilch/basimilch-app,basimilch/basimilch-app