Raw Theme is made up of spacing, palette, and font family, whereas MUI theme is made of key:value pairs, each of which represents the styling of a material-ui component based on the given raw theme. In addition, the MUI theme also contains a reference to the raw theme from which it was produced.

In every material-ui component, the "state" is used for the theme, and theme is passed down using context. Within the component, theme is always accessed using state. When a component is first mounted, we check whether a theme object is passed down using context in the getInitialState() method. If one is not found, we initialize a default MUI theme based on the default (light) raw theme. Moreover, to listen for updates when the parent changes the theme, the new context is always checked in componentWillReceiveProps().

Now, the ThemeManager module simply contains functions that return new MUI theme objects (support for immutability). The theme itself (raw theme) is a plain JS object containing key:value pairs for spacing, palette, and font family. Users can easily define their own raw themes and require() them in their modules.

src/icon-button.jsx had double definitions of some functions due to human error in previous commit.