Only use 'es2015.iterable' to avoid accidental es2015 feature usage.

DanielRosenwasser · DanielRosenwasser · commit cc477ee89127 · 2018-12-10T17:46:17.000-08:00
diff --git a/src/tsconfig-base.json b/src/tsconfig-base.json
@@ -1,7 +1,7 @@
 {
     "compilerOptions": {
         "pretty": true,
-        "lib": ["es2015"],
+        "lib": ["es2015.iterable", "es5"],
         "target": "es5",
         "rootDir": ".",
 
