(new:major) Implemented "Search Items by Category" operation (to be tested).

(delete:major) Removed operations that has not been rewritten yet (e.g., sell, bid, comment).

(change:major) Renamed RegisterOperation into RegisterUserOperation to avoid confusion between the "Register User" and the "Register Item" operations (the last one is still to be implemented).
(new:major) New 'Browse Categories in Region' operation.
(new:major) New 'Search Items by Region' operation.
(bug-fix:minor) Forgot to initialize URL for 'Search Items by Region' operation.
(new:major) New 'View Item' operation.
(new:major) New 'View User Information' operation.
(new:major) New 'View Bid History' operation.
(new:major) New 'Buy Now Item' operation.
(change:minor) Use of rubis.RubisGenerator#checkHttpResponse to check the result of an HTTP response.
Ditto
(bug-fix:minor) Forget to form HTTP GET request with given parameters.