pd.cut() support set labels,but when read,labels is deprecated,use code instead
#### Code Sample, a copy-pastable example if possible

```python
# Your code here
import pandas as pd
from pandas import DataFrame,Series
ages = [20,22,25,27,21,23,37,31,61,45,41,32]
bins = [18,25,35,60,100]
group_names = ['Youth','YoungAdult','MiddleAged','Senior']
pd.cut(ages,bins,labels=group_names)

cuts.labels
/Users/****/anaconda/bin/ipython:1: FutureWarning: 'labels' is deprecated. Use 'codes' instead
  #!/Users/****/anaconda/bin/python
Out[134]: array([3, 3, 3, 2, 3, 3, 0, 2, 1, 0, 0, 2], dtype=int8)

In [135]: cuts.codes
Out[135]: array([3, 3, 3, 2, 3, 3, 0, 2, 1, 0, 0, 2], dtype=int8)
```
#### Problem description

pd.cut() support argument labels not codes
but the getter of the property support codes not labels

#### Expected Output

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

<details>

[paste the output of ``pd.show_versions()`` here below this line]
In [137]: pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.1.final.0
python-bits: 64
OS: Darwin
OS-release: 16.7.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: zh_CN.UTF-8
LOCALE: zh_CN.UTF-8

pandas: 0.20.1
pytest: 3.0.7
pip: 9.0.1
setuptools: 27.2.0
Cython: 0.25.2
numpy: 1.12.1
scipy: 0.19.0
xarray: None
IPython: 5.3.0
sphinx: 1.5.6
patsy: 0.4.1
dateutil: 2.6.0
pytz: 2017.2
blosc: None
bottleneck: 1.2.1
tables: 3.3.0
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 2.4.7
xlrd: 1.0.0
xlwt: 1.2.0
xlsxwriter: 0.9.6
lxml: 3.7.3
bs4: 4.6.0
html5lib: 0.999
sqlalchemy: 1.1.9
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None

</details>
