Impacted versions:10

Steps to reproduce:
Following the code in https://www.odoo.com/documentation/10.0/api_integration.html both in a fresh install and against 'https://demo.odoo.com/start' trows a type error

Current behavior:
Now I get an error when executing:

```
ids = models.execute_kw(db, uid, password,  'res.partner', 'search',
    [[['is_company', '=', True], ['customer', '=', True]]],
    {'limit': 1})
[record] = models.execute_kw(db, uid, password,
    'res.partner', 'read', [ids])
# count the number of fields fetched by default
len(record)
```

In particular it seems to be a type error (cannot marshal class odoo.tools.float_utils.float_precision)

Expected behavior:
I would expect it to behave as in the documentation

openerp/fields.py
converters = [(name, value._fields[name].convert_to_onchange)
                      for name in fnames if name != 'id']
        result = [(5,)]
        for record in value:
            vals = {name: convert(record[name], record) for name, convert in converters}
            if not record.id:
                result.append((0, 0, vals))
            elif vals:
                result.append((1, record.id, vals))
            else:
                result.append((4, record.id))
        return result
    def convert_to_export(self, value, record):