Pull request for Calfw-org.el

An entry which has period info(example:* <2011-8-1 Mon>--<2011-8-2 Tue> Going back to home town) is displayed as a long string likes "<2011-08-01 Mon>--<2011-08-02 Tue> back to home town".
I think it is too long for a limited space on calendar buffer. 
I can only see "<2011-08-01 Mon>--<2011-08-02..." on calendar buffer.
So, I modified function cfw:org-extract-summary to remove a part which matchs org-tr-regexp from org-item.