Merge pull request #20 from michaelfung/master

fix params typo in device api
Merge pull request #21 from michaelfung/master

add device type codes lookup table
Merge pull request #22 from michaelfung/master

add error codes lookup table
Merge pull request #23 from michaelfung/master

fix params in user_hub
modify the change keys API
Merge branch 'master' of https://github.com/michaelfung/hu.git
make params consistent in set key