Update neural_gpu documentation.
Update neural_gpu documentation.

* 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.
wangyang59/tf_models,beomyeol/models,alexgorban/models,wangyang59/tf_models,nathansilberman/models,tombstone/models,jch1/models,bousmalis/models,xcyan/models,r888888888/models,xcyan/models,jch1/models,jiaphuan/models,jiaphuan/models,derekjchow/models,sshleifer/object_detection_kitti,jazcollins/models,calberti/models,jch1/models,sshleifer/object_detection_kitti,wangyang59/tf_models,bousmalis/models,jiaphuan/models,r888888888/models,cshallue/models,beomyeol/models,derekjchow/models,jazcollins/models,wangyang59/tf_models,xcyan/models,hang-qi/models,alexgorban/models,xcyan/models,tombstone/models,jch1/models,clinc/models,derekjchow/models,cshallue/models,tombstone/models,cshallue/models,tombstone/models,jazcollins/models,hang-qi/models,tombstone/models,zbigniewwojna/text-rcnn,jazcollins/models,tombstone/models,alexgorban/models,renjinghai/models,derekjchow/models,xcyan/models,bousmalis/models,sshleifer/object_detection_kitti,nathansilberman/models,r888888888/models,wangyang59/tf_models,jazcollins/models,hang-qi/models,wangyang59/tf_models,nathansilberman/models,hang-qi/models,hang-qi/models,calberti/models,jch1/models,alexgorban/models,r888888888/models,jiaphuan/models,r888888888/models,xcyan/models,clinc/models,jazcollins/models,beomyeol/models,cshallue/models,bousmalis/models,alexgorban/models,derekjchow/models,hang-qi/models,clinc/models,bousmalis/models,jiaphuan/models,bousmalis/models,sshleifer/object_detection_kitti,r888888888/models,renjinghai/models,cshallue/models,jiaphuan/models,sshleifer/object_detection_kitti,jch1/models,calberti/models,sshleifer/object_detection_kitti,renjinghai/models