Used as a backend in blockchat

See the original for the tutorial on this.

• Supports conversation between two people (instead of a common chat room)
• Added coins
• Encryption of messages using RSA Public-Private Key pairs
• Transactions are stored to a file instead of using only memory
• Transactions file is asynchronously uploaded to a Firebase Storage container
• Tried to eliminate race condition when two users send a message simulatenously
• Ready to be deployed to Heroku