Add methods to resize the tabs to fit the browser window

### Description
Currently, most tabs on the AI2 design page such as Palette and Properties are not allowed to be resized to fit the browser window. It may cause some troubles when users try to narrow the browser window to do something else like reading an toturial at the same time.

I made some modification to make the size of the tabs adjust automatically when the size of browser window is changed.

### Screen Shots:
* FormEditorScreen_Before
![4](https://f.cloud.github.com/assets/6442245/2178097/6415b990-9657-11e3-960f-65668d7bd782.png)

* FormEditorScreen_After
![3](https://f.cloud.github.com/assets/6442245/2178099/6c14eb48-9657-11e3-8dd6-c711da3359b3.png)

* BlocksEditorScreen_Before
![6](https://f.cloud.github.com/assets/6442245/2178103/91750800-9657-11e3-84c4-b32548a247fc.png)

* BlocksEditorScreen_After
![5](https://f.cloud.github.com/assets/6442245/2178112/e2ad93fe-9657-11e3-8551-c6a84cd1cadc.png)