Allow read_csv to take URLs
This allows read_csv to take URLs. The tests are going to need to be modified after it's merged to point the the new repo URL or if you want to host a test file somewhere else. I also have no idea what the file:// path should be on non-posix systems, so this path might need some adjustment. Not sure. There's no test case for ftp, but I don't see why it wouldn't work the same as http.
