Fix curl flag to follow redirects

This is totally super minor, but it looks like at least on my version of curl the `-F` flag is for form params or something. I think we need `-L` to follow redirects instead.

Here's my curl version incase it's just broken for me:

```
curl 7.24.0 (x86_64-apple-darwin12.0) libcurl/7.24.0 OpenSSL/0.9.8r zlib/1.2.5
```