Go back to previous dir to no fail on relative paths

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

gitstats

 		for gitpath in args[0:-1]:
 			print 'Git path: %s' % gitpath
 
+			prevdir = os.getcwd()
 			os.chdir(gitpath)
 
 			print 'Collecting data...'
 			data.collect(gitpath)
 
+			os.chdir(prevdir)
+
 		print 'Refining data...'
 		data.saveCache(cachefile)
 		data.refine()