BUG/ENH : Column name mangling doesn't strip white space
#### A small, complete example of the issue

```
a ,a ,a 
1,2,3
4,5,6
7,8,9
```

note the white space next to the char.

``` python
>>> import pandas
>>> df = pandas.read_table('test.csv', sep=',')
>>> df.columns
Index([u'a ', u'a .1', u'a .2'], dtype='object')
```

again, note the white space between the char and the num.

A work around previously was to set `mangle_dupe_cols` to `False`, manually strip the columns and then clean up the column names. With `pandas 0.19.0`, `mangle_dupe_cols=False` raises a `ValueError`.

This issue is more of a question as to what the spec of `mangle_dupe_cols` is and what a full implementation, mentioned in https://github.com/pydata/pandas/issues/13262 , desires/is going to be.
#### Expected Output

``` python
Index([u'a', u'a.1', u'a.2'], dtype='object')
```
#### Output of `pd.show_versions()`

<details>
## INSTALLED VERSIONS

commit: None
python: 2.7.11.final.0
python-bits: 64
OS: Darwin
OS-release: 15.6.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: en_US.UTF-8
LANG: en_US.UTF-8
LOCALE: None.None

pandas: 0.19.0
nose: 1.3.7
pip: 8.1.2
setuptools: 23.1.0
Cython: 0.24
numpy: 1.10.4
scipy: None
statsmodels: None
xarray: None
IPython: 5.1.0
sphinx: 1.4.1
patsy: None
dateutil: 2.5.2
pytz: 2016.3
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: 2.4.0
xlrd: 1.0.0
xlwt: None
xlsxwriter: None
lxml: 3.6.0
bs4: 4.4.1
html5lib: 0.999
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: None
boto: None
pandas_datareader: None
</details>
