newline defaults for read_csv and write_csv are not consistent
It's possible to write out a CSV file using the default settings (i.e., `line_terminator='\n'` in `DataFrame.to_csv`) that can't be read back in using the default settings (i.e., `lineterminator=None`).  

This problem arises when there's a text column that doesn't get quotes around it (e.g., if it has no commas) but has a carriage return.   `read_csv` by default thinks that either '\n' or '\r' can be line terminators, so extra rows appear.  See example below.

```
In [12]: pd.DataFrame({"text": ["foo\rbar"]}).to_csv("foo.csv", index=False)

In [13]: pd.read_csv("foo.csv")
Out[13]: 
  text
0  foo
1  bar
```

It might be best to have the default line terminator for `read_csv` be '\n'.    That might reduce usability (e.g., it's nice to be able to load CSVs from UNIX or Windows using the defaults), so maybe it'd be good just to add something to the documentation.  Or, maybe a warning could be printed out or exception raised if a CSV file appears to use multiple types of line endings, which shouldn't happen.

(IIRC this can also cause the default parsing engine to make python segfault in some cases.)
