Write CSV without index as default
#### Code Sample, a copy-pastable example if possible

Most of the time when I write a csv to file I don't need the index in the CSV output. I end up writing `to_csv('file/path.csv', index=False)` basically everytime. I am wondering if `Index=False` should be the default.
#### Expected Output

`pd.to_csv('file/path.csv')`
#### output of `pd.show_versions()`

commit: None
python: 2.7.10.final.0
python-bits: 64
OS: Darwin
OS-release: 15.0.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.17.1
nose: 1.3.7
pip: 7.1.2
setuptools: 1.1.6
Cython: None
numpy: 1.10.4
scipy: 0.17.0
statsmodels: None
IPython: 4.0.0
sphinx: None
patsy: None
dateutil: 2.4.2
pytz: 2015.7
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: 1.5.0
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.4.1
html5lib: 1.0b8
httplib2: 0.9.2
apiclient: None
sqlalchemy: 1.0.10
pymysql: None
psycopg2: None
Jinja2: None
