Added first portion of logging adaptation.

Things may be broken at this point - there are still several modules to
be adapted.

ebook_converter/ebooks/txt/txtml.py

@@ -64,7 +64,7 @@ class TXTMLizer(object):
         output = [u'']
         output.append(self.get_toc())
         for item in self.oeb_book.spine:
-            self.log.debug('Converting %s to TXT...' % item.href)
+            self.log.debug('Converting %s to TXT...', item.href)
             for x in item.data.iterdescendants(etree.Comment):
                 if x.text and '--' in x.text:
                     x.text = x.text.replace('--', '__')