UnicodeDecodeError with Latin-1 characters in Stata files
#### Steps to reproduce

```python
df = pd.read_stata('buggy_file.dta')
```
#### Expected behaviour

Pandas reads the stata file just fine.

#### Actual behaviour 

Pandas raises an error to do with encoding, traceable back to this line: 

#### Diagnosis

The error is caused by the “smart quote” character <kbd>“</kbd>, which is encoded in Latin-1 in the Stata `.dta` file, but it considered an invalid byte sequence in Unicode.

The errors originates in the `StataReader` class in `io/stata.py`:

```python
    def _decode(self, s):
        s = s.partition(b"\0")[0]
        return s.decode('utf-8')
```

Instead of `'utf-8'`, Pandas should use `self._encoding or self._default_encoding`, just like other parts of the code use when reading from the input buffer/file. Making the relevant change on my machine makes the issue go away.

#### Output of ``pd.show_versions()``

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.5.5.final.0
python-bits: 64
OS: Darwin
OS-release: 17.7.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.20.3
pytest: None
pip: 10.0.1
setuptools: 39.2.0
Cython: None
numpy: 1.13.1
scipy: 0.19.1
xarray: None
IPython: 6.1.0
sphinx: 1.6.3
patsy: None
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 2.0.2
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.6.0
html5lib: 0.9999999
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None

</details>
