README updates:

- Remove reference to Flow;
- Add TypeScript to "supported language features";
- Remove irrelevant deployment docs;
- Remove reference to ejecting;

package.json

@@ -22,7 +22,6 @@
     "eslint": "4.10.0",
     "eslint-config-react-app": "^2.1.0",
     "eslint-loader": "1.9.0",
-    "eslint-plugin-flowtype": "2.39.1",
     "eslint-plugin-import": "2.8.0",
     "eslint-plugin-jsx-a11y": "5.1.1",
     "eslint-plugin-react": "7.4.0",