When parsing a CSV file without an index, if the list with columns names is too short or too long, one gets a "Index contains duplicate entries" exception.
Hi Wes,

Just a minor bug submisson:
When parsing a CSV file without an index, if the list with columns names is too short or too long, one gets a "Index contains duplicate entries" exception.

E.g.:

The file test.csv contains:
abc,1,a
abc,2,b
def,3,c

Running:
`table = pandas.read_csv('reports/9/test.csv', header=None, names=['a', 'b'],index_col=None)`
## Results in:

``` python
Exception                                 Traceback (most recent call last)
/home/marius/Code/otsquant/analysis/ccapital/<ipython-input-70-7f388b2776b2> in <module>()
----> 1 table = pandas.read_csv('reports/9/test.csv', header=None, names=['a', 'b'],index_col=None)

/usr/lib64/python2.7/site-packages/pandas/io/parsers.pyc in read_csv(filepath_or_buffer, sep, header, index_col, names, skiprows, na_values, parse_dates, date_parser, nrows, iterator, chunksize, skip_footer, converters, verbose, delimiter, encoding)
    125         return parser
    126 
--> 127     return parser.get_chunk()
    128 
    129 @Appender(_read_table_doc)

/usr/lib64/python2.7/site-packages/pandas/io/parsers.pyc in get_chunk(self, rows)
    467         if not index._verify_integrity():
    468             dups = index.get_duplicates()
--> 469             raise Exception('Index has duplicates: %s' % str(dups))
    470 
    471         if len(self.columns) != len(zipped_content):

Exception: Index has duplicates: ['abc']
```

Many thanks,
Marius
