restructure reusable sources into package format

[jmzhao]

Proposed structure could be like

./
|- titanic/ # all reuseable sources as a package
  |- __init__.py
  |- data/ # modules about data parsing and processing
    |- __init__.py
    |- Dataset.py 
    ...
  |- nn/ # modules about NN
    |- __init__.py
    |- model.py
    ...
|- data/ # dataset and processed data
  |- original/
    |- xxx.csv
    ...
|- visualize
  |- xxx.ipynb
|- README.md
...

[dolremi]

Files have been reconstructed.