Add Neural Machine Translation example, fix URLs 
Add Neural Machine Translation example, fix URLs 

Add Neural Machine Translation with Transformers/Reformers example to the README.md file and replace the URLs from https://github.com/google/trax/blob/master/examples/ to https://github.com/google/trax/blob/master/trax/examples/ Adding /trax so it works.
google/trax,google/trax