don't create js test directories unless they are being used

just moves a setup block from `__init__` to `launch`
Merge pull request #5083 from minrk/one-nb-server

don't create js test directories unless they are being used
Updating JS tests README.md.
Merge pull request #5078 from ellisonbg/js-readme

Updating JS tests README.md
Fix incorrect usage of attrs
Revert "Fix incorrect usage of attrs"

This reverts commit 04aa0885bb143fd0409fe133ca572004ffa6dc0e.
Let backbone get changed attrs
Revert "Let backbone get changed attrs"

This reverts commit 4dd4990ff146508894353e390601c659d2638ed3.
Added test that shows the problem.
Fixed typo in new test
Only send diff message if diff isn't corrupt.

Diff will corrupt if more then one model.set(...) call is made
before model.save (or view.touch() in our case).
Keep a running diff instead of forcing a full state update
Fixed typo