v0.2 (02/03/2015)
** User **
	Add referers_diff display plugin
	Add year statistics in month details
	Add analysis duration
	Add browsers detection
	Add operating systems detection
	Add track users plugin
	Add feeds plugin
	Add _append feature to conf.py
	Add hours_stats plugin

** Dev **
	Add istats_diff interface

** Bugs **
	Forgot <body> tag
	Bad UTC time computation
	Hits/pages in the same second where not analyzed
	Last day of month was skipped