Change file mode of shell scripts under script directory

644 ->
755
Add a base class of Model

This class and derived classes can be used by Amon2::Plugin::Model.
Add a model class for threads of board
Test: Move an 'use' statement into subtest block
Add a method that gets a thread data using an id of thread
Add a method that gets responses attached to a thread using a thread id
Remove a needless constructor
Merge pull request #10 from oguro1021/model_thread

Thread の Model