Documentation examples of SSL config options; closes #116

I'm embarrassed.  I got the RCurl and httr documentation mixed up and didn't realize I was back in the httr section (where you anticipated my question in the previous post).  How do you feel about this snippet replacing the second and third examples above?  

When does a client have to use `config()` instead of passing the options directly?

Also, would it be better to send them to the [cURL](http://curl.haxx.se/libcurl/c/curl_easy_setopt.html) page instead of the [libcurl](http://linux.die.net/man/3/curl_easy_setopt) page that's specific to Linux (& Mac I guess)?  I don't see anything that the Linux version has that the cURL version doesn't.  Or am I misunderstanding how RCurl works?

```
#See the 'Details' section above for available CURL options.
#  In this case, use HTTPS with the SSL certificates provided in httr.
#   
curl_options <- config(sslversion = 3)

result_2 <- GET(url = "https://google.com", config = curl_options)
result_2$status_code

#Configuration options can be specified directly, without config().
result_3 <- GET("https://google.com", sslversion = 3)
```