SeekBarPreference: make formatter an explicit property instead of using the extras bundle.

android/src/com/reecedunn/espeak/SeekBarPreference.java

     private int mProgress = 0;
     private int mMin = 0;
     private int mMax = 100;
+    private String mFormatter = "%s";
 
     public void setProgress(int progress) {
         mProgress = progress + mMin;
         return mMax;
     }
 
+    public void setFormatter(String formatter) {
+        mFormatter = formatter;
+    }
+
+    public String getFormatter() {
+        return mFormatter;
+    }
+
     public SeekBarPreference(Context context, AttributeSet attrs, int defStyle)
     {
         super(context, attrs, defStyle);

android/src/com/reecedunn/espeak/TtsSettingsActivity.java

         switch (parameter.getUnitType())
         {
             case Percentage:
-                pref.getExtras().putString("formatter", context.getString(R.string.formatter_percentage));
+                pref.setFormatter(context.getString(R.string.formatter_percentage));
                 break;
             case WordsPerMinute:
-                pref.getExtras().putString("formatter", context.getString(R.string.formatter_wpm));
+                pref.setFormatter(context.getString(R.string.formatter_wpm));
                 break;
             default:
                 throw new IllegalStateException("Unsupported unit type for the parameter.");
                                 summary = entries[index].toString();
                             }
                         } else if (preference instanceof SeekBarPreference) {
-                            String formatter = preference.getExtras().getString("formatter");
+                            final SeekBarPreference seekBarPreference = (SeekBarPreference) preference;
+                            String formatter = seekBarPreference.getFormatter();
                             summary = String.format(formatter, (String)newValue);
                         }
                         preference.setSummary(summary);