handle multiple successive primitives in primitivegroups

could be done prettier once https://github.com/mafintosh/protocol-buffers/issues/3 is resolved
fix primitivegroup sub-bufs
push arrays
parse*() don't need be members
parse relations
parse denseinfo + way & relation info
revive warning on unknown primitive

will signal when you should implement parsing node, not only densenodes
disable test for now
1.2.0