Downgrade terser until terser/terser#254 is merged

Author: bhollis

Diff for: package.json

@@ -99,6 +99,7 @@
     "tslint-config-prettier": "^1.17.0",
     "tslint-eslint-rules": "^5.1.0",
     "tslint-react": "^3.5.1",
+    "terser": "3.14.1",
     "typescript": "^3.0.0",
     "url-loader": "^1.1.1",
     "webpack": "^4.5.0",

Diff for: yarn.lock

@@ -9188,7 +9188,7 @@ source-map-resolve@^0.5.0:
     source-map-url "^0.4.0"
     urix "^0.1.0"
 
-source-map-support@^0.5.3, source-map-support@^0.5.7, source-map-support@^0.5.9, source-map-support@~0.5.9:
+source-map-support@^0.5.3, source-map-support@^0.5.7, source-map-support@^0.5.9, source-map-support@~0.5.6, source-map-support@~0.5.9:
   version "0.5.10"
   resolved "https://registry.yarnpkg.com/source-map-support/-/source-map-support-0.5.10.tgz#2214080bc9d51832511ee2bab96e3c2f9353120c"
   integrity sha512-YfQ3tQFTK/yzlGJuX8pTwa4tifQj4QS2Mj7UegOu8jAz59MqIiMGPXxQhVQiIMNzayuUSF/jEuVnfFF5JqybmQ==
@@ -9606,6 +9606,15 @@ terser-webpack-plugin@^1.1.0:
     webpack-sources "^1.1.0"
     worker-farm "^1.5.2"
 
+terser@3.14.1:
+  version "3.14.1"
+  resolved "https://registry.yarnpkg.com/terser/-/terser-3.14.1.tgz#cc4764014af570bc79c79742358bd46926018a32"
+  integrity sha512-NSo3E99QDbYSMeJaEk9YW2lTg3qS9V0aKGlb+PlOrei1X02r1wSBHCNX/O+yeTRFSWPKPIGj6MqvvdqV4rnVGw==
+  dependencies:
+    commander "~2.17.1"
+    source-map "~0.6.1"
+    source-map-support "~0.5.6"
+
 terser@^3.8.1:
   version "3.16.0"
   resolved "https://registry.yarnpkg.com/terser/-/terser-3.16.0.tgz#04028e6e5da461d91691cedd75fa53a17f2f20d9"