Updates XLA to 00afc7bb81.
The new XLA release removes the use of protocol buffers from the XLA client. Fixes#349.
Add backward compatibility shims to jaxlib to allow older jax releases to still work on an up to date jaxlib.
The new XLA release also incorporates a fix that avoids a host-device copy for every iteration of a `lax.fori_loop()` on GPU. Fixes#402.
Add a new jaxlib.__version__ field, change jax/jaxlib compatibility logic to check for it.
An alternative to installing `jax` using `pip install -e .` is to use `python setup.py`. This creates build/ and dist/ directories that should not be included in diffs since they are meant to be local.
This PR adds those entries to the .gitignore file
