remove old external.js

this is unused and old, and we no longer ship custom minified-only js.
Added working speaker notes for slides.
Fixing docs.
Fixing info in trailets.
add keyboard shortcut to docs, closes #2960
Escape filename for pdflatex, otherwise filenames with spaces cause issues.
update CodeMirror component to 3.15
Merge pull request #3864 from ivanov/fix-2960

add keyboard shortcut to docs

closes #2960
Merge pull request #3861 from minrk/external-js

remove old external.js
Add new filter tests
Remove noise in test output
Fix fuzzy compare logic
Add leave_padding option to fuzzy compare
Added highlight tests
Fixed highlight test for latest pygments
Silence INFO logging in test output
Use built in test comparison
Fix assert_equal ref
Provide a list of the command and argument to subprocess for PDF post-processor, which is a better way to avoid issues if there are spaces in the filename.
Fixed double single apostrophe