Merge pull request #1 from mkouhei/devel

Adding "GET" method and some updates.
Adding get_* API

 * Added next api methods.
   - get tasks
   - get task
   - get categories
   - get category (this method returns status code only)
 * Change method name.
   - user_info to get_user_info

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>