Add value and type check for mib get/set function

Signed-off-by: leo-ma <begeekmyfriend@gmail.com>
Improve coding style

Signed-off-by: leo-ma <begeekmyfriend@gmail.com>
Spelling mistake

Signed-off-by: leo-ma <begeekmyfriend@gmail.com>
Merge pull request #36 from leo-ma/rsp_val_check

Check the type of return value for MIB get/set function.