switch from zip-stream to yazl
update to yazl 1
yazl 2. zipfile download shows accurate progress now.
client: fix player prediction regression from 415ae5a7
reorder dependencies to avoid merge conflicts later
switch from jsondiffpatch to curlydiff
don't need deleteUndefineds anymore
yazl 2.0.1. fix 'write after end' error
Merge branch 'yazl'

Conflicts:
	package.json
multifile downloads use url parameters.

no need for body-parser dependency.
fixing zipfile name when multiple artists or albums are selected.
closes #339.
Merge branch 'master' into curlydiff
update curlydiff