Allow specifying a Picasso instance to use

Add methods to allow configuring the Picasso instance used by the slider
when it loads images.

Author: kojustin

library/src/main/java/com/daimajia/slider/library/SliderTypes/BaseSliderView.java

@@ -47,6 +47,8 @@ public abstract class BaseSliderView {
 
     private String mDescription;
 
+    private Picasso mPicasso;
+
     /**
      * Scale type of the image.
      */
@@ -205,7 +207,7 @@ public void onClick(View v) {
             mLoadListener.onStart(me);
         }
 
-        Picasso p = Picasso.with(mContext);
+        Picasso p = (mPicasso != null) ? mPicasso : Picasso.with(mContext);
         RequestCreator rq = null;
         if(mUrl!=null){
             rq = p.load(mUrl);
@@ -304,4 +306,23 @@ public interface ImageLoadListener{
         public void onEnd(boolean result,BaseSliderView target);
     }
 
+    /**
+     * Get the last instance set via setPicasso(), or null if no user provided instance was set
+     *
+     * @return The current user-provided Picasso instance, or null if none
+     */
+    public Picasso getPicasso() {
+        return mPicasso;
+    }
+
+    /**
+     * Provide a Picasso instance to use when loading pictures, this is useful if you have a
+     * particular HTTP cache you would like to share.
+     *
+     * @param picasso The Picasso instance to use, may be null to let the system use the default
+     *                instance
+     */
+    public void setPicasso(Picasso picasso) {
+        mPicasso = picasso;
+    }
 }