add English translation of code part for word2vec

Refine image classification doc

English translation for code part of chapter machine translation

refine recommender_system/README.en.md

Fix README.en.md in MNIST for jupyter.

Fix README.en.md in SRL for jupyter.

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