add catching exceptions
implements set_config and get_config with zookeeper.
jubaconfig is a command line tool that set/get config data from zookeeper.
don't use not statement
Merge branch 'develop' into feature/zkcommand

Conflicts:
	src/common/membership.cpp
	src/common/wscript
	tools/generator/keeper_generator.ml
implement set_config from file or zookeeper.

implement three functions as follow,
void config_fromlocal(const std::string&, pfi::text::json::json&);
void config_fromzk(lock_service& , const std::string& , const std::string& , pfi::text::json::json&);
void config_tozk(lock_service& , const std::string& , const std::string& , pfi::text::json::json&);
Remove classifier_factory class and change create_classifier method to a normal method.

Conflicts:

	src/server/classifier_serv.cpp
Change classifier factory interface

Conflicts:

	src/server/classifier_serv.cpp
Remove regression_factory class and add regression namespace

Conflicts:
	src/server/regression_serv.cpp
fix to latest develop branch.

	modified:   src/classifier/classifier_factory.cpp
	modified:   src/classifier/classifier_factory.hpp
	modified:   src/classifier/classifier_test.cpp
	modified:   src/regression/regression_factory.cpp
	modified:   src/regression/regression_factory.hpp
	modified:   src/regression/regression_factory_test.cpp
	modified:   src/server/classifier_serv.cpp
add JSON to regression factory
fix regression namespace

jubatus::regression::hogehoge.
refactoring classifier namespace.

same as recommender, regression
add json to string function in util.cpp
fix config using json (regression)
fix get_json function
classifier set config from json
add default param of get_jsonstring

string get_jsonstring(json, key, default);
Add param to recommender factory interface.
Remove old interface of classifier factory.
Remove old interface of regression factory