add attribute #tsb_thumb_text_distance control the thumbText's distance

[jdpxiaoming]

add attribute #tsb_thumb_text_distance control the thumbText's distance to thumb icon .
see img .

<com.warkiz.tickseekbar.TickSeekBar
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tsb_progress="88"
            app:tsb_show_thumb_text="above"
            app:tsb_thumb_color="@color/color_blue"
            app:tsb_thumb_text_color="@color/color_pink"
            app:tsb_track_progress_color="@color/color_blue"
            app:tsb_tick_texts_size="8sp"
            app:tsb_thumb_text_distance="5dp"
            />