[WiDi API] Fix the issue for the relative url passed to requestShow.

If a relative url is passed to requestShow, the page can not be opened correctly.
Fix it by resolving the url with base url to make it to be an absolute one.
Merge pull request #7 from kurli/xdk-int-resolve-relative-url

[WiDi API] Fix the issue for the relative url passed to requestShow.