Add additional padding for MSF with external tools

This will allow the external tools to fully show given the
module sequence footer is floating at the bottom now.

closes CNVS-26677

Test Plan:
  - Load up a course with TurnitIn enabled
  - Add an external tool to a module
  - As a student take a look at the module
  - The footer should not cover the "accept/reject" buttons
    for TurnitIn.
    * Note: This must be done at a lower resolution as it doesn't
            affect larger screens since they have plenty of screen
            real estate.

Change-Id: I3ae25cf3cc1e31dfd69cab3246afeaf8eb41aff8
Reviewed-on: https://gerrit.instructure.com/71042
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Clare Strong <clare@instructure.com>
Tested-by: Jenkins
Product-Review: Clay Diffrient <cdiffrient@instructure.com>

app/stylesheets/base/_module_sequence_footer.scss

@@ -33,6 +33,10 @@
   #content {
     &.Content--with-module-footer {
       padding-bottom: 70px;
+
+      .tool_content_wrapper {
+        padding-bottom: 70px;
+      }
     }
   }