alias/rename carmel package

[miyagawa]

Because the word package in Perl has some special meaning (namespaces), carmel package might not be the most obvious choice when people try to look for this command.

In Carton, this is implemented as carton bundle. I could simply alias the bundle subcommand to package.

I think vendor is an attractive choice as well e.g. carmel vendor, though to me "vendoring modules" sounds more of importing it to vendor/lib and maintain the fork.

Bundler seems to call it bundle cache.