TensorFlow: a few small updates.
TensorFlow: a few small updates.

Changes:
- Fix softmax formula in word2vec to remove an extra exp()
  by @gouwsmeister

- Python3 fixes to remove basestring / support for unicode by @mrry

- Remove some comments by Josh

- Specify exact versions of bower dependencies for TensorBoard by
  @danmane.

Base CL: 107742361

ioeric/tensorboard,qiuminxu/tensorboard,shakedel/tensorboard,shakedel/tensorboard,ioeric/tensorboard,agrubb/tensorboard,agrubb/tensorboard,tensorflow/tensorboard,francoisluus/tensorboard-supervise,qiuminxu/tensorboard,ioeric/tensorboard,tensorflow/tensorboard,francoisluus/tensorboard-supervise,tensorflow/tensorboard,tensorflow/tensorboard,ioeric/tensorboard,tensorflow/tensorboard,qiuminxu/tensorboard,shakedel/tensorboard,shakedel/tensorboard,shakedel/tensorboard,francoisluus/tensorboard-supervise,agrubb/tensorboard,tensorflow/tensorboard,shakedel/tensorboard,ioeric/tensorboard,francoisluus/tensorboard-supervise,agrubb/tensorboard,ioeric/tensorboard,tensorflow/tensorboard,francoisluus/tensorboard-supervise,agrubb/tensorboard,qiuminxu/tensorboard,qiuminxu/tensorboard,qiuminxu/tensorboard,agrubb/tensorboard,francoisluus/tensorboard-supervise