Moved code from namespace jubatus::exception to namespace jubatus::core::common::exception.
Moved code in key_manager* from namespace jubatus to namespace jubatus::core::common.
Moved code in jubatus/core/common/type.hpp and jubatus/core/common/vector_util.[ch]pp
from namespace jubatus to namespace jubatus::core::common.
Moved hash_util and portable_mixer from namespace jubatus to namespace jubatus::core::common.
Moved code in jubatus/core/common/jsonconfig from namespace jubatus::core::jsonconfig to jubatus::core::common::jsonconfig.
Modified code to pass cpplint.
Merge pull request #345 from gwtnb/namespace-core-common

Fixed namespace of types under jubatus/core/common (#335).