README update

gh-pages deploy

Refactored: styled components moved to separate files under [root_component_name].styles.js for better code readability

Refactored dropdown component

Implemented CSS Transitition Group component to dropdown

Fixed: listView re-render on filtered done/important change

Updated styles for navigation filter count

Fixed: markDone / markImportant data rerender

Added navigation/filter menu

Added dropdown component

Added context API, markDone, markImportant setter functions

Implementing context API

Initial commit