Code improvements

[AndreyKozlov1984]

• eslint would allow to spot common typos and issues. It helps a lot with react development.

• redux-thumb helps with async actions in redux and makes it easy to specify the workflow

• server could use koa2, because it is an express with async/await, thus no more callbacks or promises. The code becomes easier to read.

• server could use a latest syntax with babel-node, like it is done on a client side.

• react-virtualized could display large amount of items in the grid without possible performance issues, although it really helps starting from 1000 or more rows in the grid.

• flow-typed or typescript would add types, reducing amount of typos even more, but increase the complexity of a project.

[AndreyKozlov1984]

Done, except the koa2, even with express async/await makes the code easier to read.