Update bootstrap (#246)

Fixes several XSS

Author: Wardormeur

package.json

@@ -21,7 +21,7 @@
   },
   "dependencies": {
     "@coderdojo/cd-common": "1.1.11",
-    "bootstrap": "^3.3.7",
+    "bootstrap": "^3.4.1",
     "cp-translations": "1.0.124",
     "font-awesome": "^4.7.0",
     "handlebars": "^4.1.0",

yarn.lock

@@ -1171,9 +1171,9 @@ [email protected]:
   dependencies:
     hoek "2.x.x"
 
-bootstrap@^3.3.7:
-  version "3.3.7"
-  resolved "https://registry.yarnpkg.com/bootstrap/-/bootstrap-3.3.7.tgz#5a389394549f23330875a3b150656574f8a9eb71"
+bootstrap@^3.4.1:
+  version "3.4.1"
+  resolved "https://registry.yarnpkg.com/bootstrap/-/bootstrap-3.4.1.tgz#c3a347d419e289ad11f4033e3c4132b87c081d72"
 
 boxen@^0.6.0:
   version "0.6.0"