Use "stable" tag on npm for master builds and "latest" for develop/smoke

This is different of what it is currently, where master/smoke goes to "latest" and develop goes to "develop"

Export costumes and sounds!

Update scratch-vm to the latest version 

Update scratch-blocks to the latest version 

Only update the toolbox when the blocks tab is visible.

Update project changes test 

Update scratch-l10n to the latest version 

Update scratch-blocks to the latest version 

Menus should be over most things

Update scratch-vm to the latest version 

Update project changes test to test a project change that should actually emit a change event. Clicking on blocks should not emit a project changed event.

fixes https://github.com/LLK/scratch-www/issues/2587
and https://github.com/LLK/scratch-gui/issues/4428

changed menu-bar z-index to one more than monitors so drop down menus cover monitors when opened.

This invalidates the toolbox XML when switching back to the code tab after e.g. renaming a costume, making the code tab

I know we will want to change this eventually, so I added comments about that. But the next commit originally contained an inadvertent change to this functionality, so I wanted to add an integration test so that when we do change it, we

It looks like an "test.only" was left in on one of these tests by mistake.

Update scratch-vm to the latest version 

Need to store the rendered xml because the props can change while the blocks tab is hidden, but we re-render based on what was rendered, not the previous props (which may not have been rendered).

This is similar to the `ThrottledPropertyHOC` in that there may be prop changes that do not get rendered, but in this case for a different reason.

This increases the performance of switching between code and other editor tabs, as well as improving the "See Inside" performance. It makes switching to the code tab as fast as switching between sprites.

Avoid double toolbox update on mount and when setting language

Move rounding into sprite info to improve performance

chore(package): update scratch-vm to version 0.2.0-prerelease.2019012…

Update scratch-render to the latest version 

Update scratch-vm to the latest version 

Update scratch-blocks to the latest version