to_csv with lists of strings and unicode encoding produces wrong output
If I have a dataframe with cells containing lists of strings (or unicode strings), then these lists are broken when I use `to_csv()` with the `encoding` parameter set. The error does not occur if the `encoding` is not set.

Here is an example (using pandas version 0.16.2):

```
df = pd.DataFrame.from_records(
    [('Mary S.',['Detroit, MI','New York, NY']),
     ('John U.',[u'Atlanta, GA',u'Paris, France'])],
    columns=['name','residences'])
df.to_csv('ascii.csv')
df.to_csv('utf8.csv',encoding='utf-8')
```

The ascii-encoded CSV file is fine. (contents of 'ascii.csv' below)

```
,name,residences
0,Mary S.,"['Detroit, MI', 'New York, NY']"
1,John U.,"[u'Atlanta, GA', u'Paris, France']"
```

But the unicode CSV file fails to quote the strings within the lists. (contents of 'utf8.csv' below)

```
,name,residences
0,Mary S.,"[Detroit, MI, New York, NY]"
1,John U.,"[Atlanta, GA, Paris, France]"
```

This results in the data being impossible to recover. For example, if I load this file using `read_csv()`, the relevant cells are treated as strings, and cannot be accurately recast as lists.

The behavior is the same using `encoding='utf-16'` but I didn't check any other encodings.
