df autosorts rows on construction with OrderedDict of OrderedDicts
```python

from collections import OrderedDict
import pandas as pd
data = OrderedDict([('ele2', OrderedDict([('b', 1), ('a', 2)])),
                    ('ele1', OrderedDict([('b', 2), ('a', 5)]))])             
pd.DataFrame(data)
```
![capture](https://user-images.githubusercontent.com/832380/32543581-53bb0d4c-c476-11e7-8b7d-c9c9089663da.PNG)
#### Problem description
The output shows the rows get sorted. 

#### Expected Output

When constructing a df with OrderedDicts I would expect the order in columns *and* rows to stay the same. 

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

<details>
In [6]: pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.13.final.0
python-bits: 64
OS: Linux
OS-release: 3.10.0-514.21.1.el7.x86_64
machine: x86_64
processor:
byteorder: little
LC_ALL: C
LANG: en_US.UTF-8A
LOCALE: None.None

pandas: 0.21.0
pytest: None
pip: 9.0.1
setuptools: 27.2.0
Cython: 0.25.2
numpy: 1.12.1
scipy: 0.19.0
pyarrow: None
xarray: None
IPython: 5.3.0
sphinx: 1.6.2
patsy: 0.4.1
dateutil: 2.6.0
pytz: 2017.2
blosc: None
bottleneck: None
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: 3.8.0
bs4: None
html5lib: 0.999
sqlalchemy: 1.1.10
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
