gofmt; make it go gettable

This change gofmts the code to the usual standard,
and makes it possible to "go get github.com/xetorthio/etcd-fs"
with no need to run make. There are no semantic changes
other than the one mentioned below.

There is one externally visible change here, which
is that the name of the executable created by "go get"
is named after the github repo, so it's "etcd-fs" not "etcdfs".

If this is a problem there are two ways to solve it:
1) move the executable code down one level, so the
"go get" path becomes github.com/xetorthio/etcd-fs/etcdfs
or 2) rename the repo to etcdfs.