Update title of GPU Computing introduction

Fix image link in README.md for GPU libraries

Fix image link in README for CUDA libraries

Update link to Open Hackathon page

Update salloc command for GPU connection

Update Top 500 supercomputer list date in README

Fix link to CUDA C++ Programming Guide

Revise title of GPU computing introduction

Revise GPU resources section in README

Update README.md

Update README.md

Update README.md

Update README.md

Update README.md

Update README.md