GitLab

* Switch from decimal to symbol in most places and add a description of what a symbol is per Lukasz.

* Add list of algorithmic tasks.
* Detail what is stored in /tmp/neural_gpu/ (default location).
* Detail that one should hit Ctrl-C to stop the training process.
* Add sections around decoding and animation, but couldn't get those to work myself. Still worth having in the docs.

* `python neural_gpu_trainer.py --task=rev` raises the following TypeError:

  File “..models/neural_gpu/neural_gpu.py", line 26, in conv_linear
    assert args
  File “..tensorflow/python/framework/ops.py", line 475, in __nonzero__
    raise TypeError("Using a `tf.Tensor` as a Python `bool` is not allowed. "
TypeError: Using a `tf.Tensor` as a Python `bool` is not allowed. Use `if t is not None:` instead of `if t:` to test if a tensor is defined, and use the logical TensorFlow ops to test the value of a tensor.