Delete single IP support & bug fixes

This adds support for deleting a single IP from an asset provided your
collins version has been kept up to date. Additionally it has a bug fix
that would cause the CLI to panic if your asset had a huge amount of
storage.

Commits since last tag

eb72b82 Add single IP delete support
3ff4a35 Update deps
c0c4de5 Allow commas for modify -d flag
266ce7a Fixup for issue 50