Memory registry from #801 with additional tweaks (#951)

* PoC: memory registry using maps instead of slice madness

* Updated proto and handlers. Fixed tests across codebase.

* Implemented ttl pruning for memory registry

* Added extensive memory registry tests

* Squased a bunch of bugs

* Proto indent; memory.Registry.String() returns "memory"

* Write a test to prove memory registry TTLs are busted

Signed-off-by: Erik Hollensbe <github@hollensbe.org>

* Additional memory testing and fixups:

* DefaultTTL removed
* When TTL == 0, it is automatically removed from expiry conditions
* Additional improvements to new tests

Signed-off-by: Erik Hollensbe <github@hollensbe.org>

broker/http_broker_test.go

@@ -7,15 +7,13 @@ import (
 
 	glog "github.com/go-log/log"
 	"github.com/google/uuid"
+	"github.com/micro/go-micro/registry"
 	"github.com/micro/go-micro/registry/memory"
 	"github.com/micro/go-micro/util/log"
 )
 
-func newTestRegistry() *memory.Registry {
-	r := memory.NewRegistry()
-	m := r.(*memory.Registry)
-	m.Services = testData
-	return m
+func newTestRegistry() registry.Registry {
+	return memory.NewRegistry(memory.Services(testData))
 }
 
 func sub(be *testing.B, c int) {