fix dead link, modify license in Readme.en.md

Fix image_classification/README.md

Fix README.md

refine index page

Try to fix typeset in machine translation.

fix typeset and bad link in SRL.

update image for mnist

rename reader_dict to feeding

fix softmax formula

change url in pre-commit-config

use v2 attr and pooling

Auto convert html and ipynb in pre commit

Add more checks into .pre-commit-config

2nd pass for translating chapter1.

Change fit_a_line/README.en.md according to changes in README.md