add condition - log speed change / loading video
add unit test for speed_change_video event
Allow multiple client-side runtimes on a single page

Make XBlock client-side runtimes proper classes, so that handlerUrl can
be defined in a per-runtime way, and we can have multiple runtimes on a
single page.

[LMS-1630][LMS-1421][LMS-1517]
Converted <ol> to <div> to prevent a11y confusion.
The default course CSS class should be empty string rather than None.
Doc Update for Component label in editable unit page

for STUD-1242
Make Studio load XBlock fragment js and css on the client-side

[LMS-1421][LMS-1517]
Make uses of quote_slashes always operate on encoded strings
Merge pull request #2307 from edx/jbau/allow-unset-course-startdate

Handle taking registrations on a course with TBD start date
Install Python prereqs before running doc and i18n tests
Merge pull request #2469 from edx/will/doc-and-i18n-test-prereqs

Install Python prereqs before running doc and i18n tests
Merge pull request #2412 from edx/bugfix/ichuang/formulaequation-msg2

add message output to formulaequationinput.html (capa)
Increase wait time in XQueue stub test
Merge pull request #2358 from Szczork/szczork/log-speed-change-video

add condition - log speed change / loading video
Merge pull request #1949 from cpennington/xblock-studio-js-and-css

Enable XBlock js and css in Studio
Add docs about testing xblocks in the LMS

[LMS-2059]
[LMS-2060]
[LMS-1216]
Merge pull request #2470 from edx/will/fix-http-stub-test

Increase wait time in XQueue stub test
Make tab nav page object more robust
Merge pull request #2464 from edx/dcs/default-css-class

The default course CSS class should be empty string rather than None.
Merge pull request #2449 from cpennington/xblock-testing-docs

Add docs about testing xblocks in the LMS