Convert ThemeEditor to JS class syntax
Convert ThemeEditor to JS class syntax

Change-Id: I6a37c8e94b5d42b8b3e1b1080eb459d1d49a5348
Reviewed-on: https://gerrit.instructure.com/135545
Reviewed-by: Ryan Shaw <ea3cd978650417470535f3a4725b6b5042a6ab59@instructure.com>
Tested-by: Jenkins
QA-Review: Tucker McKnight <4b51b98c1d84aa97854d216bd061ce5d3eda8a28@instructure.com>
Product-Review: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>

sfu/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,djbender/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,djbender/canvas-lms