Abandon Closure Compiler in favor of UglifyES (#2285)

Moved to UglifyES, ditched async cruft, clarified responsibilities between cli & minify.

Makes for faster, more reliable, synchronous, non-Google-reliant minification.

package-lock.json

@@ -1972,6 +1972,30 @@
       "integrity": "sha1-hnrHTjhkGHsdPUfZlqeOxciDB3c=",
       "dev": true
     },
+    "uglify-es": {
+      "version": "3.3.9",
+      "resolved": "https://registry.npmjs.org/uglify-es/-/uglify-es-3.3.9.tgz",
+      "integrity": "sha512-r+MU0rfv4L/0eeW3xZrd16t4NZfK8Ld4SWVglYBb7ez5uXFWHuVRs6xCTrf1yirs9a4j4Y27nn7SRfO6v67XsQ==",
+      "dev": true,
+      "requires": {
+        "commander": "~2.13.0",
+        "source-map": "~0.6.1"
+      },
+      "dependencies": {
+        "commander": {
+          "version": "2.13.0",
+          "resolved": "https://registry.npmjs.org/commander/-/commander-2.13.0.tgz",
+          "integrity": "sha512-MVuS359B+YzaWqjCL/c+22gfryv+mCBPHAv3zyVI2GN8EY6IRP8VwtasXn8jyyhvvq84R4ImN1OKRtcbIasjYA==",
+          "dev": true
+        },
+        "source-map": {
+          "version": "0.6.1",
+          "resolved": "https://registry.npmjs.org/source-map/-/source-map-0.6.1.tgz",
+          "integrity": "sha512-UjgapumWlbMhkBgzT7Ykc5YXUT46F0iKu8SGXq0bcwP5dz/h0Plj6enJqjz1Zbq2l5WaqYnrVbwWOWMyF3F47g==",
+          "dev": true
+        }
+      }
+    },
     "uglify-js": {
       "version": "2.8.29",
       "resolved": "https://registry.npmjs.org/uglify-js/-/uglify-js-2.8.29.tgz",