pd.read_excel parse_dates not implemented
#### Code Sample, a copy-pastable example if possible

```
conda create -n pandas18 python=3.5 pandas xlrd ipython
```

``` python
In [1]: import pandas as pd

In [2]: pd.__version__
Out[2]: '0.18.0'

In [3]: url='https://github.com/chris1610/pbpython/raw/master/data/sales-feb-2014.xlsx'

In [4]: pd.read_excel(url, parse_dates=True, index_col='date').info()
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)
<ipython-input-4-636dbf8d885a> in <module>()
----> 1 pd.read_excel(url, parse_dates=True, index_col='date').info()

/Users/adefusco/Applications/anaconda3/envs/p18/lib/python3.5/site-packages/pandas/io/excel.py in read_excel(io, sheetname, header, skiprows, skip_footer, index_col, names, parse_cols, parse_dates, date_parser, na_values, thousands, convert_float, has_index_names, converters, engine, squeeze, **kwds)
    175         convert_float=convert_float, has_index_names=has_index_names,
    176         skip_footer=skip_footer, converters=converters,
--> 177         squeeze=squeeze, **kwds)
    178 
    179 

/Users/adefusco/Applications/anaconda3/envs/p18/lib/python3.5/site-packages/pandas/io/excel.py in _parse_excel(self, sheetname, header, skiprows, skip_footer, index_col, has_index_names, parse_cols, parse_dates, date_parser, na_values, thousands, convert_float, verbose, squeeze, **kwds)
    308                                       "is not implemented")
    309         if parse_dates:
--> 310             raise NotImplementedError("parse_dates keyword of read_excel "
    311                                       "is not implemented")
    312 

NotImplementedError: parse_dates keyword of read_excel is not implemented
```
#### Expected Output

```
conda install pandas=0.17
```

``` python
In [1]: import pandas as pd

In [2]: pd.__version__
Out[2]: '0.17.1'

In [3]: url='https://github.com/chris1610/pbpython/raw/master/data/sales-feb-2014.xlsx'

In [4]: pd.read_excel(url, parse_dates=True, index_col='date').info()
<class 'pandas.core.frame.DataFrame'>
DatetimeIndex: 108 entries, 2014-02-01 09:04:59 to 2014-02-28 23:47:32
Data columns (total 6 columns):
account number    108 non-null int64
name              108 non-null object
sku               108 non-null object
quantity          108 non-null int64
unit price        108 non-null float64
ext price         108 non-null float64
dtypes: float64(2), int64(2), object(2)
memory usage: 5.9+ KB
```
#### output of `pd.show_versions()`
## INSTALLED VERSIONS

commit: None
python: 3.5.1.final.0
python-bits: 64
OS: Darwin
OS-release: 14.5.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.18.0
nose: None
pip: 8.1.1
setuptools: 20.3
Cython: None
numpy: 1.10.4
scipy: None
statsmodels: None
xarray: None
IPython: 4.1.2
sphinx: None
patsy: None
dateutil: 2.5.0
pytz: 2016.1
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: 0.9.4
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: None
boto: None
