Support N distributed agents

This is the third main feature of this system. The code needs a bunch of
polish, but it actually all works :)

I've tested this briefly with N <= 3.

Currently you have to build your own etcd cluster. It's quite easy, just
run `etcd` and it will be ready. I usually run it in a throw away /tmp/
dir so that I can blow away the stored data easily.

misc.go

@@ -27,10 +27,21 @@ import (
 
 // Similar to the GNU dirname command
 func Dirname(p string) string {
+	if p == "/" {
+		return ""
+	}
 	d, _ := path.Split(path.Clean(p))
 	return d
 }
 
+func Basename(p string) string {
+	_, b := path.Split(path.Clean(p))
+	if p[len(p)-1:] == "/" { // don't loose the tail slash
+		b += "/"
+	}
+	return b
+}
+
 // Split a path into an array of tokens excluding any trailing empty tokens
 func PathSplit(p string) []string {
 	return strings.Split(path.Clean(p), "/")