GitLab

Update README.md compile instructions to match adding_an_op.
from [adding_an_op](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/docs_src/extend/adding_an_op.md).

Tested: compiled using the modified instructions and ran `python word2vec_optimized_test.py`.

Fixes tensorflow/tensorflow#14620

tf.contrib.framework.get_or_create_global_step -> tf.train.get_or_create_global_step

CIFAR website is now using https.
Since urllib does not follow the http to https redirection and thus never retrieves any data, the data URL needs an update.

Trying to remove the +1.

This will error when num_gpus > 1

example_pos_ is the cursor to current position when reading the corpus file. When corpus file is very big, the corpus_size_ may bigger than max of int32, then example_pos_ became negative, and cause `corpus_[example_pos_]` to `Segmentation Fault`.