fixing build script (#15)

Author: NiranjanaBinoy

package.json

@@ -4,10 +4,10 @@
   "description": "Simple stream multiplexing for objectMode.",
   "main": "dist/index.js",
   "files": [
-    "dist"
+    "dist/"
   ],
   "scripts": {
-    "build": "tsc --project .",
+    "build": "rm -rf ./dist && tsc --project .",
     "lint": "eslint . --ext ts,js,json",
     "lint:fix": "yarn lint --fix",
     "test": "yarn build && node test",