1. Remove illustration of arguments.
2. Make inference support for more format input.

1. Add document.
2. Add arguments for saving model and init model.
3. Refine inference.py and eval.py.
4. Make ctc_reader.py support for custom data.

1. Add download of data into ctc_read.py
2. Use 'clone' instead of 'get_inference_program'
3. Add time to train log

2. Add inference script
3. Add load model script
4. Add some functions into ctc_reader