TypeError when subtracting from empty index
#### Code Sample, a copy-pastable example if possible

While `pd.DataFrame().index + 1` returns the unchanged index `Index([], dtype='object')`,
I see the following error with subtraction:

```python
In [71]: pd.DataFrame().index - 1
Traceback (most recent call last):

  File "<ipython-input-71-cbb1aa99c0f9>", line 1, in <module>
    pd.DataFrame().index - 1

  File "C:\Program Files\WinPython-64bit-3.5.2.3Qt5\python-3.5.2.amd64\lib\site-packages\pandas\indexes\base.py", line 1796, in __sub__
    "{typ}".format(typ=type(self)))

TypeError: cannot perform __sub__ with this index type: <class 'pandas.indexes.base.Index'>
```
#### Problem description

I would like to have `pd.DataFrame().index - 1` return the unchanged index, too.
The current behavior makes my code not generalize well for the edge case of empty dataframes (which happen in my environment).

#### Expected Output

The same as in the summation case.

#### Output of ``pd.show_versions()``
<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.5.2.final.0
python-bits: 64
OS: Windows
OS-release: 7
machine: AMD64
processor: Intel64 Family 6 Model 42 Stepping 7, GenuineIntel
byteorder: little
LC_ALL: None
LANG: en
LOCALE: None.None

pandas: 0.19.1
nose: 1.3.7
pip: 8.1.2
setuptools: 28.7.1
Cython: 0.25.1
numpy: 1.11.2
scipy: 0.18.1
statsmodels: 0.8.0rc1
xarray: 0.8.2
IPython: 5.1.0
sphinx: 1.4.8
patsy: 0.4.1
dateutil: 2.5.3
pytz: 2016.7
blosc: 1.4.4
bottleneck: 1.2.0
tables: 3.3.0
numexpr: 2.6.1
matplotlib: 1.5.3
openpyxl: None
xlrd: 1.0.0
xlwt: None
xlsxwriter: 0.9.3
lxml: 3.6.4
bs4: 4.5.1
html5lib: 0.999999999
httplib2: None
apiclient: None
sqlalchemy: 1.1.3
pymysql: None
psycopg2: None
jinja2: 2.8
boto: None
pandas_datareader: 0.2.1
</details>
