Replace UnicodeDecodeErrors caused by Python2 readline() method.

 * CHANGE gnupg._meta.GPGBase.__init__() to register the builtin
   `codecs.replace_errors` handler and a global codecs "strict" error
   handler.
 * FIXES Issue #49:
   https://github.com/isislovecruft/python-gnupg/issues/49
Merge branch 'fix/49-unicode-decode-on-readline' into develop