Redirect to non-HTTP URI yields NoMethodError

[michieldewit]

When calling the following:

 FastImage.size 'http://world-of-nlp.net/favicon.ico'

This will yields a NoMethodError exception on https://github.com/sdsykes/fastimage/blob/master/lib/fastimage.rb#L301.

The problem is that the original URL leads to a number of redirects, eventually ending at hhttp://www.world-of-nlp.net, which is a valid URI, but not a HTTP URL. As such the URI will get parsed, but it will be parsed to a URI::Generic instance rather than a URI::HTTP instance as FastImage expects when trying to call request_uri on it. Hence the NoMethodError.

It would probably best to add a check like @parsed_uri.is_a? URI::HTTP. Such a check would also be better then checking the scheme property as is being done in initialize().