Update bootstrap version

package.json

@@ -3,11 +3,11 @@
   "version": "0.1.0",
   "private": true,
   "dependencies": {
-    "bootstrap": "3",
+    "bootstrap": "3.4.0",
     "dompurify": "^1.0.3",
     "markdown-it": "8.4.1",
     "react": "16.5.0",
-    "react-bootstrap": "0.32.4",  
+    "react-bootstrap": "0.32.4",
     "react-dom": "16.5.0",
     "react-helmet": "5.0.3",
     "react-router-dom": "4.3.1",

yarn.lock

@@ -1280,9 +1280,10 @@ boom@2.x.x:
   dependencies:
     hoek "2.x.x"
 
-bootstrap@3:
-  version "3.3.7"
-  resolved "https://registry.yarnpkg.com/bootstrap/-/bootstrap-3.3.7.tgz#5a389394549f23330875a3b150656574f8a9eb71"
+bootstrap@3.4.0:
+  version "3.4.0"
+  resolved "https://registry.yarnpkg.com/bootstrap/-/bootstrap-3.4.0.tgz#f8d77540dd3062283d2ae7687e21c1e691961640"
+  integrity sha512-F1yTDO9OHKH0xjl03DsOe8Nu1OWBIeAugGMhy3UTIYDdbbIPesQIhCEbj+HEr6wqlwweGAlP8F3OBC6kEuhFuw==
 
 boxen@^0.6.0:
   version "0.6.0"