etcdhttp: attach clusterID to key and adminMember endpoint
pkg: move everything into subpackages
Merge pull request #1426 from xiangli-cmu/clusterid

etcdhttp: attach clusterID to key and adminMember endpoint
Merge pull request #1428 from jonboulle/subpackages

pkg: move everything into subpackages
etcdserver: parse context error for better message
Merge pull request #1422 from unihorn/187

etcdserver: parse context error for better message
client: move Member models to new types pkg
httptypes: use []string for Member URLs
httptypes: use MemberCollection for JSON (de)serialization
client: simplify MembersAPI response parsing
httptypes: add doc.go