Series.to_string ignores empty lines at the start/end when index=False
When running `to_string` on a Series with empty strings at the beginning and end of the Series data, the empty strings are removed from the resulting output. These empty strings should be included to represent the empty data.
#### Code Sample:

``` python
import pandas as pd
pd.Series(["", "Hello", "World", "", "", "Mooooo", "", ""]).to_string(index=False) 
```
#### Expected Output:

``` python
u'\nHello\nWorld\n     \n     \nMooooo\n\n'
```
#### Actual Output:

``` python
u'Hello\nWorld\n     \n     \nMooooo'
```
#### `pd.show_versions()`:

```
>> pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.8.final.0
python-bits: 64
OS: Linux
OS-release: 3.0.101-0.47.67-default
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.18.1
nose: 1.3.6
pip: 1.5.6
setuptools: 3.6
Cython: 0.24
numpy: 1.10.4
scipy: 0.17.0
statsmodels: 0.6.1
xarray: 0.7.2
IPython: 4.2.0
sphinx: 1.2.2
patsy: 0.3.0
dateutil: 2.3
pytz: 2015.4
blosc: None
bottleneck: 1.0.0
tables: 3.2.2
numexpr: 2.4
matplotlib: 1.5.1
openpyxl: 2.0.4
xlrd: 0.9.0
xlwt: 0.7.4
xlsxwriter: 0.7.3
lxml: 3.4.4
bs4: 4.3.2
html5lib: 1.0b8
httplib2: None
apiclient: None
sqlalchemy: 0.9.7
pymysql: 0.6.2.None
psycopg2: None
jinja2: 2.8
boto: 2.34.0
pandas_datareader: None
```
