fix(etcd): use golang conventions on package names

This is a painful change but we should probably do it before we get too
far along.

"Another convention is that the package name is the base name of its
source directory; the package in src/pkg/encoding/base64 is imported as
"encoding/base64" but has name base64, not encoding_base64 and not
encodingBase64."

http://golang.org/doc/effective_go.html#package-names