Series `sort_index` missing `kind` keyword
#### A small, complete example of the issue

``` python
>>> import pandas as pd
>>> pd.Series(index=[3,2,1,4,3]).sort_index(kind='mergesort')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: sort_index() got an unexpected keyword argument 'kind'

```
#### Expected Output

A `Series` sorted by the index, i.e.:

``` python
>>> pd.Series(index=[3,2,1,4,3]).sort_index()
1   NaN
2   NaN
3   NaN
3   NaN
4   NaN
dtype: float64
```
#### Output of `pd.show_versions()`

<details>
## INSTALLED VERSIONS

commit: None
python: 2.7.6.final.0
python-bits: 64
OS: Linux
OS-release: 4.4.0-42-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.18.1
nose: 1.3.1
pip: 1.5.4
setuptools: 3.3
Cython: 0.20.1post0
numpy: 1.11.0
scipy: 0.13.3
statsmodels: None
xarray: None
IPython: 1.2.1
sphinx: 1.2.2
patsy: None
dateutil: 2.5.3
pytz: 2016.4
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: 1.3.1
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: 0.8.7
lxml: None
bs4: 4.4.1
html5lib: 0.999
httplib2: 0.8
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.7.2
boto: None
pandas_datareader: None
</details>
