name property changes unexpectedly after Series.append
Hi, I have tried Series.append but the name property changes unexpectedly.

```python
a = pd.Series(name='a')
b = pd.Series(name='b')
c = pd.Series()

# a.name turns to be None if a.name is different with b.name
a.append(b) # a.name is None after append

# a.name turns to be None if c dose not have a name
a.append(c) # a.name is None after append

# a.name remains unchanged
a.append(pd.Series(name=a.name)) # a.name dose not change

```
#### Problem description

As a new series is appended to an old one, the name of the old series should be unchanged.
This should not be satisfied only when the name of the new series is explicitly specified.
However, the above problem happens.

#### Expected Output

Whenever a.append(b) or a.append(c) is done, a.name should remain unchanged, which is 'a'.

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

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.5.1.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.19.1
nose: 1.3.7
pip: 8.1.2
setuptools: 19.2
Cython: 0.23.4
numpy: 1.11.0
scipy: 0.17.0
statsmodels: 0.6.1
xarray: None
IPython: 4.1.2
sphinx: 1.3.1
patsy: 0.4.0
dateutil: 2.5.1
pytz: 2016.2
blosc: None
bottleneck: 1.0.0
tables: 3.2.2
numexpr: 2.5.1
matplotlib: 1.5.1
openpyxl: 2.3.2
xlrd: 0.9.4
xlwt: 1.0.0
xlsxwriter: 0.8.4
lxml: 3.6.0
bs4: 4.4.1
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.0.12
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.39.0
pandas_datareader: None

</details>
