Revert "Moved JS in front of HTML"

This reverts commit 8b0164edde418138d4e28c20d63fa422931ae6a8.
Revert "Removed Javascript from Markdown by adding display priority to def config."

This reverts commit 58e05f9625c60f8deba9ddf1c74dba73e8ea7dd1.
Revert "Add Javascript to display priority of base nbconvert class."

This reverts commit 695b844ebc8f3d7c69e4d81335b2ad0b7ebb96f6.
Added Javascript to HTML exporter's display priority list