DOC: pd.read_csv doc-string clarification
need to update the docs for `read_csv` to match the doc-string. Let's make sure they have the same text / examples as much as possible (and are in the same order and such).

In particular, the `header` option doesn't have `header='infer'` which is the default in the docs, but it exists in the doc-string.

Further, should show what this does:

```
       if kwds.get('header', 'infer') == 'infer':
            kwds['header'] = 0 if kwds.get('names') is None else None
```

meaning if the the `header` kw is not specified, this it is set to the first line if no `names` are specified, else `None`.
