[Security] Bump bootstrap from 3.3.7 to 3.4.0

Bumps [bootstrap](https://github.com/twbs/bootstrap) from 3.3.7 to 3.4.0. **This update includes security fixes.**
- [Release notes](https://github.com/twbs/bootstrap/releases)
- [Commits](https://github.com/twbs/bootstrap/compare/v3.3.7...v3.4.0)

Signed-off-by: dependabot[bot] <support@dependabot.com>
Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

package-lock.json

@@ -1398,9 +1398,9 @@
       "dev": true
     },
     "bootstrap": {
-      "version": "3.3.7",
-      "resolved": "http://registry.npmjs.org/bootstrap/-/bootstrap-3.3.7.tgz",
-      "integrity": "sha1-WjiTlFSfIzMIdaOxUGVldPip63E="
+      "version": "3.4.0",
+      "resolved": "http://registry.npmjs.org/bootstrap/-/bootstrap-3.4.0.tgz",
+      "integrity": "sha512-F1yTDO9OHKH0xjl03DsOe8Nu1OWBIeAugGMhy3UTIYDdbbIPesQIhCEbj+HEr6wqlwweGAlP8F3OBC6kEuhFuw=="
     },
     "brace-expansion": {
       "version": "1.1.11",

package.json

@@ -25,7 +25,7 @@
     "autosize": "^4.0.2",
     "backbone": "^1.2.3",
     "blueimp-md5": "^2.7.0",
-    "bootstrap": "^3.3.7",
+    "bootstrap": "^3.4.0",
     "clipboard": "^1.7.1",
     "css-vars-ponyfill": "^1.7.2",
     "davclient.js": "git+https://github.com/owncloud/davclient.js.git#0.1.2",