Add support for fog streaming uploads

[chrisdurtschi]

Fog supports streaming uploads if passed a File object.
Added SanitizedFile#to_file method that returns a File object.
This works for file system based SanitizedFile (File, Tempfile, Hash, etc)
StringIO must still be read into memory before being passed to fog.

[trevorturk]

@geemus would you mind reviewing this?

[geemus]

It seems like this should perhaps use is_path? for consistency with read.

[chrisdurtschi]

I think that exists? will work better here. is_path? will return false for a SanitizedFile created from either a File or Tempfile object, which means that the entire contents will be read into memory before being passed to fog.

This code will needlessly create a new File object if @file is already a File. Maybe I should change the first line to this:

return @file if @file.is_a?(File)

[geemus]

Other than that one thing it looks good (basically the main difference is passing a file handle, ie File.open(path) instead of string and it certainly does this.).

[geemus]

Seems reasonable I think.

[trevorturk]

Thanks for looking @geemus.

@chrisdurtschi I'm getting lots of test failures. Did you run the full test suite with your changes?

     Failure/Error: @fog_file = @storage.store!(@file)
     TypeError:
       can't convert Tempfile into String

Please re-open this pull request or open a new pull request if/when you have time to fix things.

[chrisdurtschi]

Sorry, I only tested in 1.9.2. I'm getting these same failures in 1.8.7. I'll look into it and send a new pull request.

[trevorturk]

Thanks!