public void setVerticalSpacing(int pixelSize) {
        mVerticalSpacing = pixelSize;
    }
FlowLayout is much more like a {@link android.widget.LinearLayout}, but it can automatically
separate the widgets wrapped in it into multiple lines just like the water flow.

Inspired by {@see http://hzqtc.github.io/2013/12/android-custom-layout-flowlayout.html}

@author liangfeizc {@see http://www.liangfeizc.com}
flowlayout/src/main/java/com/liangfeizc/flowlayout/FlowLayout.java