Series.plot should label y axis with Series name
#### Code Sample, a copy-pastable example if possible

```python
import pandas as pd
import matplotlib.pyplot as plt
ind = pd.Series(['first', 'second', 'third'], name='count')
s = pd.Series([1, 2, 3], index=ind, name='i should be a y label')
s.plot()
plt.show()
```
#### Problem description

So when you call Series.plot, xlabel is set to the name of the index, but ylabel is not set to the name of the series itself. To me it seems asymmetric and believe it should set ylabel automatically.
Also, if I plot it with `s.plot(kind='hist')`, I get ylabel "Frequency" but no xlabel, which I would expect to be the name of the series as well.

#### Expected Output

ylabel set to name of the series for usual plot, and xlabel set to name of the series for hist plot

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

<details>

[paste the output of ``pd.show_versions()`` here below this line]
INSTALLED VERSIONS
------------------
commit: None
python: 3.6.2.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: AMD64 Family 16 Model 4 Stepping 3, AuthenticAMD
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.20.3
pytest: 3.2.1
pip: 9.0.1
setuptools: 36.5.0.post20170921
Cython: 0.26.1
numpy: 1.13.1
scipy: 0.19.1
xarray: None
IPython: 6.1.0
sphinx: 1.6.3
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 2.4.8
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 0.9.8
lxml: 3.8.0
bs4: 4.6.0
html5lib: 0.999999999
sqlalchemy: 1.1.13
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None

</details>
