compile.py: Remove date from iCalendar SUMMARY

Reported by Matt Davis:

On Sat, Dec 29, 2012 at 08:18:13PM -0800, Matt wrote:
> The events in http://software-carpentry.org/bootcamps.ics have the
> date in their `SUMMARY` field, e.g. `SUMMARY:University of Oslo\,
> Sep 17-18\, 2012`. The summary field is used in the embedded Google
> calendar and the date adds a lot of text and makes it look
> crowded. This is on a calendar so it shouldn't be necessary to
> repeat the date in the summary.
Merge pull request #169 from wking/calendar-no-dates

Remove dates from calendar event summaries
Putting an image on the home page and using multi-column layout
Merge pull request #170 from gvwilson/master

Making home page a little more attractive
bootcamps/index.html: Fix 'experience..' typo
Merge pull request #172 from wking/experience-typo

bootcamps/index.html: Fix 'experience..' typo
Removing CSS 'blueprint' package
Merge pull request #173 from gvwilson/master

Removing css/blueprint
Fixing missing </div> tag
Merge pull request #174 from gvwilson/master

Fixing missing </div> tag
Merging the latest changes to 3_0 and 4_0
Merge pull request #176 from gvwilson/master

Syncing 3_0 and 4_0