Re-enable testing with Safari and IE / Edge

With the use of iframes for all qunit tests, I had to turn off Safari and IE in karma.conf-sauce.js. I would expect they'll work fine if I'd just add some option somewhere to allow javascript from the parent window to access the iframe.

Start with karma.conf-sauce.js and the QUnit tests that now run through iframes. Investigate how Safari and IE/Edge handle parent-window access to those frames and identify the configuration option needed. Done means Sauce-based testing is enabled for Safari and IE/Edge without breaking the existing iframe test setup.

Written by the indexing model from the issue text.