to_parquet method should accept index=False option

[scottlittle]

Code Sample, a copy-pastable example if possible

# for example, index should be accepted, like so:
df.to_parquet( 'my_parquet_file.parquet', compression='gzip', index=False )

Problem description

[this should explain why the current behaviour is a problem and why the expected output is a better solution.]

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Expected Output

Output of pd.show_versions()

INSTALLED VERSIONS

commit: None
python: 3.6.4.final.0
python-bits: 64
OS: Linux
OS-release: 3.16.0-77-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.22.0
pytest: 3.2.5
pip: 9.0.1
setuptools: 39.0.1
Cython: 0.28.1
numpy: 1.14.2
scipy: 0.19.1
pyarrow: None
xarray: None
IPython: 6.2.1
sphinx: 1.7.2
patsy: 0.5.0
dateutil: 2.7.2
pytz: 2018.3
blosc: None
bottleneck: None
tables: None
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 2.5.1
xlrd: 1.0.0
xlwt: None
xlsxwriter: None
lxml: 4.2.1
bs4: 4.6.0
html5lib: 0.999999999
sqlalchemy: 1.2.5
pymysql: None
psycopg2: 2.7.4 (dt dec pq3 ext lo64)
jinja2: 2.10
s3fs: None
fastparquet: 0.1.4
pandas_gbq: None
pandas_datareader: None