fix: revert bolt/core dependency updates + temporarily remove yarn.lo…

…ck to ensure a fresh install on Travis

packages/core/package.json

@@ -7,30 +7,30 @@
   "style": "styles/index.scss",
   "repository": "https://github.com/bolt-design-system/bolt/tree/master/packages/core",
   "dependencies": {
-    "@polymer/polymer": "^3.3.0",
+    "@polymer/polymer": "^3.2.0",
     "@webcomponents/custom-elements": "^1.2.4",
     "@webcomponents/shadydom": "^1.6.0",
     "@webcomponents/template": "^1.4.0",
     "@webcomponents/webcomponentsjs": "^2.2.10",
-    "ajv": "^6.10.1",
+    "ajv": "^6.10.0",
     "change-case": "^3.1.0",
     "classnames": "^2.2.6",
-    "color": "^3.1.2",
-    "core-js": "^3.1.4",
+    "color": "^3.1.1",
+    "core-js": "^3.1.2",
     "document-register-element": "^1.13.2",
-    "element-closest": "^3.0.1",
-    "es6-promise": "^4.2.8",
-    "get-own-property-symbols": "^0.9.3",
+    "element-closest": "^2.0.2",
+    "es6-promise": "^4.2.6",
+    "get-own-property-symbols": "^0.9.2",
     "html-element": "^2.3.0",
-    "lit-element": "^2.2.0",
-    "lit-html": "^1.1.1",
+    "lit-element": "^2.1.0",
+    "lit-html": "^1.1.0",
     "lodash.merge": "^4.6.1",
-    "mdn-polyfills": "^5.17.1",
+    "mdn-polyfills": "^5.16.3",
     "preact": "8.4.2",
-    "preact-compat": "^3.19.0",
+    "preact-compat": "^3.18.5",
     "pwa-helpers": "^0.9.1",
     "raf": "^3.4.1",
-    "redux": "^4.0.3",
+    "redux": "^4.0.1",
     "redux-thunk": "^2.3.0",
     "sass-mq": "github:bolt-design-system/sass-mq#master",
     "sassy-maps": "github:at-import/Sassy-Maps#0.x.x",