FIx Issue 44 and MInor change to the Readme file

[ChakshuGupta]

The installation steps mentioned in the Readme file were - cd ChainKeeper npm install npm start

The problem was that the main ChainKeeper directory doesn't contain the package.json file. It is inside the ChainKeeper/chainkeeper_app/. So I updated the Readme to reflect the same.

Added fsevents as an optional dependency in the package.json file to keep the npm install from giving errors.