• return ErrUnexpectedEOF when Decode input is too short (#53)

This release includes BREAKING CHANGES

• go-ipld-git is now a go-ipld-prime IPLD codec. Use Decode(na ipld.NodeAssembler, r io.Reader) error and Encode(n ipld.Node, w io.Writer) error for direct use if required.
• There is now only one Tag type, MergeTag has been removed which had a text property. Use Tag's message property instead to retrieve the tag message from a commit's mergetag. i.e. <commit>/mergetag/message instead of <commit>/mergetag/text.
• PersonInfo no longer exposes the human-readable RFC3339 format date field as a DAG node. The date and timezone fields are kept as their original string forms (to enable precise round-trips) as they exist in encoded Git data. e.g. <commit>/author/date now returns seconds in string form rather than an RFC3339 date string. Use this value and <commit>/author/timezone to reconstruct the original if needed.