Update util.py

Changed line 41 so that the logarithmic change to base 1000 formula uses log base 10  instead of natural log. this allows the denominator to be simplified to 3. Also got rid of the use of floor() inside of int() because it is redundant.
Update CHANGELOG
Merge branch 'master' of https://github.com/ramandel/pygal into ramandel-master

Conflicts:
	pygal/util.py
Merge branch 'ramandel-master'