[Docs] Add new muiTheme setup requirements to docs + readme

Problem Description

Yopp guys,

After updated to latest version (MUI = 0.15.0-beta.1, react, react-dom = 15.0.1), I caught several errors from my inspector :

1. Warning: Failed Context Types: Required context muiTheme was not specified in Paper.
2. Uncaught TypeError: Cannot read property ‘prepareStyles’ of undefined
3. Uncaught TypeError: Cannot read property ‘__reactInternalInstance$f2gyonourkjfu80wspjh5mi’ of null

Any tips help me escape from these bugs weirdo ?

Be grateful for your reply.

Versions

• Material-UI: 0.15.0-beta.1
• React: 15.0.1
• Browser: Chrome ver. 49

[horte]

This is problematic when writing tests for pure components which don’t really care about the theme. Is there a suggestion for how to solve this?

Instead of this:

_wrapper = mount(<MuiThemeProvider><Counter {..._props} /></MuiThemeProvider>)

I want to do this:

_wrapper = mount(<Counter {..._props} />)

[nathanmarks]

@newoga We need to make this loud and clear in the README/docs