README.md for better readability in Github

[jishanshaikh4]

Github supports markdown, so all the text has been moved to .md file.

• Corresponding author details moved to a table
• Appropriate linking has been done to table of contents
• Bullet points have been introduced wherever felt necessary
• Neither any additional data has been added nor anything has been deleted
• Readability has been improved multiple times as compared to the old .txt file

[fangq]

thank you! looks good, merged.