logging clean-up

- moved most constants to separate file
- sorted and cleaned-up imports
- moved logging setup to separate file

cps/fb2.py

@@ -17,7 +17,9 @@
 #  You should have received a copy of the GNU General Public License
 #  along with this program. If not, see <http://www.gnu.org/licenses/>.
 
+from __future__ import division, print_function, unicode_literals
 from lxml import etree
+
 from .constants import BookMeta