Google map integration

[kiwanami]

Selecting a schedule item with the location attribute on the calfw calendar,
one wants to open the google-map buffer for the location in other window.

http://julien.danjou.info/google-maps-el.html

Currently, calfw-ical doesn't hold the original ics data text.

Then, calfw-ical should put the text property on the ics items so as to get the original contents.

[kiwanami]

The commit 4ee6d37 enables to hold a location info.