Relaxed handling of newlines.

I came across this issue with DataFrames when parsing files when windows-style `\r\n` newlines:

Calling `readtable` on csv file like the following with `\r\n` newlines:
```CSV
"x","y"
"a","b"
```
will result in
```
1x2 DataFrame:
          x     y
[1,]    "a" "b\r"
```

(Everything in the "y" column will have a trailing `\r`)

This is simpler handling in which `\n` and `\r` alone are both treated as newlines. Since blank lines are skipped over anyway, there shouldn't be any trouble with ambiguity.