Update min required React for UNSAFE_ lifecycles (react-bootstrap#4530)

Author: wheeler

package.json

@@ -53,8 +53,8 @@
   "author": "Stephen J. Collings <[email protected]>",
   "license": "MIT",
   "peerDependencies": {
-    "react": "^0.14.9 || >=15.3.0",
-    "react-dom": "^0.14.9 || >=15.3.0"
+    "react": "^16.3.0",
+    "react-dom": "^16.3.0"
   },
   "devDependencies": {
     "@babel/cli": "^7.0.0",