Add correct handling of special csv characters

At the moment, exporting a playlist as CSV format will produce a bad value if any of video's titles (or other properties) contain a special CSV character e.g:

`deadmau5 - Sometimes Things Get, Whatever (HQ),GOzwOeONBhQ,https://youtu.be/GOzwOeONBhQ`

Because the title contains a comma, it needs to be enclosed in double quotes to avoid being treated as two separate values:

`"deadmau5 - Sometimes Things Get, Whatever (HQ)",GOzwOeONBhQ,https://youtu.be/GOzwOeONBhQ`

I'm also escaping any existing double quotes before enclosing, as this is also a requirement of the format. If you're interested, I found the standard csv requirements [here](http://tools.ietf.org/html/rfc4180).

Thanks!