directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/images/resizing.go

@@ -0,0 +1,46 @@
+package images
+
+import (
+	"bytes"
+	"image"
+	"image/gif"
+	"image/jpeg"
+	"image/png"
+
+	"github.com/chrislusf/seaweedfs/weed/glog"
+	"github.com/disintegration/imaging"
+)
+
+func Resized(ext string, data []byte, width, height int) (resized []byte, w int, h int) {
+	if width == 0 && height == 0 {
+		return data, 0, 0
+	}
+	srcImage, _, err := image.Decode(bytes.NewReader(data))
+	if err == nil {
+		bounds := srcImage.Bounds()
+		var dstImage *image.NRGBA
+		if bounds.Dx() > width && width != 0 || bounds.Dy() > height && height != 0 {
+			if width == height && bounds.Dx() != bounds.Dy() {
+				dstImage = imaging.Thumbnail(srcImage, width, height, imaging.Lanczos)
+				w, h = width, height
+			} else {
+				dstImage = imaging.Resize(srcImage, width, height, imaging.Lanczos)
+			}
+		} else {
+			return data, bounds.Dx(), bounds.Dy()
+		}
+		var buf bytes.Buffer
+		switch ext {
+		case ".png":
+			png.Encode(&buf, dstImage)
+		case ".jpg", ".jpeg":
+			jpeg.Encode(&buf, dstImage, nil)
+		case ".gif":
+			gif.Encode(&buf, dstImage, nil)
+		}
+		return buf.Bytes(), dstImage.Bounds().Dx(), dstImage.Bounds().Dy()
+	} else {
+		glog.Error(err)
+	}
+	return data, 0, 0
+}