Quotes around date and commit range to allow spaces in those fields; eg "5 months ago" for a date

Signed-off-by: Heikki Hokkanen <hoxu@users.sf.net>

gitstats

 def getlogrange(defaultrange = 'HEAD', end_only = True):
 	commit_range = getcommitrange(defaultrange, end_only)
 	if len(conf['start_date']) > 0:
-		return '--since=%s %s' % (conf['start_date'], commit_range)
+		return '--since="%s" "%s"' % (conf['start_date'], commit_range)
 	return commit_range
 
 def getcommitrange(defaultrange = 'HEAD', end_only = False):