Release 0.3: More testing coverage!

• Added tests for single part sets
• Added tests for query params sets
• Added single query param (un)setting

• Fixed query parts assignment

Release 0.2: Merging/unsetting query params made possible

• Added Url::setQueryParams() method as a wrapper around Url::setParts().
• Made unsetting query params possible.

Initial release after library split

State corresponds to the AnrDaemon/library-php@b5f8007 release.