Porting for "installcjkdict --local CEDICT"

build/builder.py
- In EDICTFormatBuilder.getFileHandle(), use a try/except block to open
  a file as gzip. Files downloaded to a temporary location (/tmp/foo)
  lose their .gz extension, so this method would use codecs.open() to
  return an file handle that was unusable.
- 'import io' only once, instead of repeatedly.
cjklib/build/builder.py: import only StringIO from io
Porting necessary to execute cjknife

cjklib/cjknife.py
- Using 2to3.

cjklib/dbconnector.py
cjklib/reading/__init__.py
- Manual porting in the codepaths used by cjknife.