Merge pull request #427 from chrox/master

add regional zoom mode in pdf/djvu page
Merge pull request #428 from chrox/master

explicitly call free method of Blitbuffer for credocument
add floating punctuation option for crereader
Luckily after disabling floating punctuation left/right margin
are able to be same now (with large enough margins, should be
more than 1em). So I also changed the default page margins for
crereader and removed the dirty hack.