ImportError: Using URI string without sqlalchemy installed.
#### Having created a new virtual environment and having installed SQLAlchemy and Pandas, I'm having trouble with the `read_sql_query` function which gives me the following error:

`ImportError: Using URI string without sqlalchemy installed.`

The code looks something like this:

``` python
URI_CONN_STRING = 'postgres://user:pass@ip-address:5432/db-name'
df = pd.read_sql_query(sql_query, URI_CONN_STRING, index_col=None, coerce_float=True, params=None, chunksize=None)

```
#### Expected Output

I'd expect to get a data frame with the results of the SQL query
#### Output of `pd.show_versions()`

<details>
## INSTALLED VERSIONS

commit: None
python: 2.7.10.final.0
python-bits: 64
OS: Darwin
OS-release: 15.2.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_GB.UTF-8
LOCALE: None.None

pandas: 0.19.0
nose: None
pip: 8.1.2
setuptools: 28.6.1
Cython: None
numpy: 1.11.2
scipy: None
statsmodels: None
xarray: None
IPython: 5.1.0
sphinx: None
patsy: None
dateutil: 2.5.3
pytz: 2016.7
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.1.2
pymysql: None
psycopg2: None
jinja2: 2.8
boto: None
pandas_datareader: None

</details>
