Release 2.6.0-rc0

Bug Fixes and Other Changes

Update __init__.py: Added a __version__ variable
Fixes the benchmark suite for graph mode. While using tf.function prevented caching, it was also causing the graph being tested to rebuild each time. Using placeholder instead fixes this.
Pin nightly version.
Remove TF patch as it is not needed anymore. The code is in core TF.
Typos
Format and lint NBs, add images
Add a couple notes to the BertTokenizer docs.
Narrative docs migration: TF Core -> TF Text
Update nmt_with_attention
Moved examples of a few API docs above the args sections to better match other formats.
Fix NBs
Update Installation from source instruction.
Add SplitterWithOffsets as an exported symbol.
Fix a note to the BertTokenizer docs.
Remove unused index.md
Convert tensorflow_text to use public TF if possible.
Fix failing notebooks.
Create user_ops BUILD file.
Remove unnecessary METADATA.
Replace tf.compat.v2.xxx with tf.xxx, since tf_text is using tf2 only.
Fix load_data function in nmt tutorial
Update tf.data.AUTOTUNE in Fine-tuning a BERT model
Switch TF to OSS keras (1/N).
added subspaces
Disable TSAN for tutorial tests that may run for >900sec when TSAN is enabled.
Adds a short description to the main landing page of our GitHub repo to point users to the tf.org subsite.
Phrasing fix to TF Transformer tutorial.
Disable RTTI when building Tf.Text kernels for mobile

This release contains contributions from many people at Google, as well as:

8bitmp3, akiprasad, bongbonglemon, Jules Gagnon-Marchand, Stonepia