Run some tests under karma

Including a regression test for
https://github.com/vector-im/vector-web/issues/1314

test/all-tests.js

@@ -0,0 +1,7 @@
+// all-tests.js
+//
+// Our master test file: uses the webpack require API to find our test files
+// and run them
+
+var context = require.context('./app-tests', true, /\.jsx?$/);
+context.keys().forEach(context);