Change peerDependencies to dependencies

Also removed some duplication.

Addresses #584

plugins/welcome/package.json

@@ -13,8 +13,6 @@
   },
   "devDependencies": {
     "@backstage/cli": "^0.1.1-alpha.4",
-    "@backstage/core": "^0.1.1-alpha.4",
-    "@backstage/theme": "^0.1.1-alpha.4",
     "@testing-library/jest-dom": "^4.2.4",
     "@testing-library/react": "^9.3.2",
     "@testing-library/user-event": "^7.1.2",
@@ -22,9 +20,9 @@
     "@types/node": "^12.0.0",
     "@types/testing-library__jest-dom": "5.0.2"
   },
-  "peerDependencies": {
-    "@backstage/core": "^0.1.1-alpha.3",
-    "@backstage/theme": "^0.1.1-alpha.3",
+  "dependencies": {
+    "@backstage/core": "^0.1.1-alpha.4",
+    "@backstage/theme": "^0.1.1-alpha.4",
     "@material-ui/core": "^4.9.1",
     "@material-ui/icons": "^4.9.1",
     "@material-ui/lab": "4.0.0-alpha.45",