refactor: Tag class support in registerTag()

src/emitters/index.ts

@@ -0,0 +1,4 @@
+export * from './emitter'
+export * from './simple-emitter'
+export * from './streamed-emitter'
+export * from './keeping-type-emitter'

src/emitters/keeping-type-emitter.ts

@@ -1,5 +1,5 @@
-import { stringify, toValue } from '../util/underscore'
-import { Emitter } from '../types'
+import { stringify, toValue } from '../util'
+import { Emitter } from './emitter'
 
 export class KeepingTypeEmitter implements Emitter {
   public buffer: any = '';

src/emitters/simple-emitter.ts

@@ -1,4 +1,4 @@
-import { stringify } from '../util/underscore'
+import { stringify } from '../util'
 import { Emitter } from './emitter'
 
 export class SimpleEmitter implements Emitter {

src/emitters/streamed-emitter.ts

@@ -1,4 +1,4 @@
-import { stringify } from '../util/underscore'
+import { stringify } from '../util'
 import { Emitter } from './emitter'
 import { PassThrough } from 'stream'