message: mention date-fns version in docs
diff: @@ -6,7 +6,7 @@ import { Typography } from 'material-ui';
  import muiPickerProviderCode from '!raw-loader!Examples/CodeSnippets/MuiPickerProviderCode';
  const installLibCode =
  -`npm i -s date-fns@next
  +`npm i -s date-fns@2.0.0-alpha.7
  // or
  npm i -s moment
  // or
  @@ -29,7 +29,13 @@ const Installation = () => (
  <a className="link" href="https://moment.github.io/luxon/"> luxon</a>. If you
  are not using moment in the project (or dont have it in the bundle already)
  we suggest using date-fns,
  - because it much more lightweight and will be correctly tree-shaked from the bundle.
  + because it is much more lightweight and will be correctly tree-shaken from the bundle.
  + </Typography>
  + <Typography variant="body1" gutterBottom>
  + Note, that we support only 2.0.0-alpha.7 version of date-fns for now (see
  + &nbsp;<a className="link" href="https://github.com/dmtrKovalenko/material-ui-pickers/issues/414#issuecomment-389523267">#414</a>
  + ).
  + Stay tuned!
  </Typography >
  <Code withMargin text={installLibCode} />
  