* Cleaned up use of section levels
* Renamed ma to multiply_add and sq_add to square_add
* Other minor clarifications
* Separated the Colabs into Tutorials and Advanced Tutorials
Using threading within a traced context still won't work, but that is perhaps less important than the ability to call JIT-ted computations from separate threads.
(Revives https://github.com/google/jax/pull/734.)