Add support for github

[athityakumar]

To-Do

• Get data from GitHub after auth via curl statements.
• Get all pages, in case of paginated data.
• Store all data into a single json file.
• Make sendmail to mail the new notifications to user's email ID.
• Add a mailing template (mail.txt.erb), to be used with sendmail command utility to mail the new notifications.
• Add an easy config.json file rather than getting input from the program itself.
• Setup a bash script to automate this locally, which can be copy-pasted on crontab.
• Deploy cron job to server like Heroku.
• Properly .gitignore credentials.