TNL-932: Add styling to Notes page.
Merge pull request #6174 from edx/anton/edxnotes-apply-ui

TNL-932: Add styling to Notes page.
make block.get_parent() work.

Co-Authored-By: Christina Roberts <christina@edx.org>
Co-Authored-By: Daniel Friedman <dfriedman@edx.org>
Co-Authored-By: Don Mitchell <dmitchell@edx.org>