Updated syntax for recipes

[amarpatel]

redux-logger is awesome, thanks for making it!

Issue

The existing recipe for Transform Immutable (with combineReducers) uses let and var when const should be used, and has an unneeded ;.

Fix

I've refactored the examples to be more functional with appropriate variable usage.

Before:

After:

[amarpatel]

The travis ci error isn't due to this change:

/home/travis/build/evgenyrodionov/redux-logger/src/core.js
  129:29  error  Strings must use singlequote  quotes