Implementing the depreciated start and end groups types

[kenttregenza]

As indicated here https://developers.google.com/protocol-buffers/docs/encoding The wire types of 3 and 4 (start and end groups) are "depreciated" ... but unfortunately they still exist on some protobuf packets floating around.

This could be easily resolved by adding these types and then update skip to include them (skipping zero bytes):
else if (type === Pbf.StartGroup) this.pos += 0;
else if (type === Pbf.EndGroup) this.pos += 0;

[bulk88]

I agree, googleapis still return start and end groups.