Conform Series.to_csv to DataFrame.to_csv
Thank you for this awesome package!

#### Problem description
When indexing/selecting/slicing a `DataFrame`, pandas may return a `Series`. Both classes support the `to_csv` method, but the methods have subtle differences. These subtle differences may break your code, or demand a call to `to_frame`. Perhaps it would be beneficial to conform the `Series.to_csv` method to the `DataFrame.to_csv` method?

At least, the following two examples seem relevant (and are the reason I came here):

- `DataFrame.to_csv` accepts the keyword parameter `path_or_buf`. This seems to be completely analogous to the differently named keyword parameter `path` of `Series.to_csv`.
- `DataFrame.to_csv` accepts the keyword parameter `line_terminator`. There does not seem to be an analogous keyword parameter of `Series.to_csv`.

* * *

Addendum: Other differences

The following two keyword parameters are implemented for `DataFrame.to_csv`, but not for `Series.to_csv`: `compression`, `chunksize`. I suppose these are mostly relevant if you have very large dataframes, but I do not see any reason why they should not have analogous methods for Series.

Some of the keyword parameters of `DataFrame.to_csv` are specific to multi-column data and may therefore not make immediate sense for `Series.to_csv`. On the other hand, a user may wish to use quoting in a single-column file in order to maintain conformity with other parts of a bigger project. In this relation, the following keyword parameters are implemented for `DataFrame.to_csv` but do not for `Series.to_csv`:  `quoting`, `quotechar`,`doublequote`, `escapechar`.

#### Output of ``pd.show_versions()``
<details>

INSTALLED VERSIONS
------------------

commit: None
python: 3.6.3.final.0
python-bits: 64
OS: Linux
OS-release: 4.13.0-32-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL:
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.22.0
pytest: None
pip: 9.0.1
setuptools: 38.5.1
Cython: None
numpy: 1.14.0
scipy: None
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: None
patsy: None
dateutil: 2.6.1
pytz: 2017.3
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: None
openpyxl: 2.5.0
xlrd: 1.1.0
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: None
s3fs: None
fastparquet: None
pandas_gbq: None
pandas_datareader: None
None
</details>
