Use overflow:auto instead of scroll

Before:
![jiren github io filter js stream html--before](https://cloud.githubusercontent.com/assets/3154126/4324750/ad3df20e-3f5d-11e4-961b-2d3a9fdd61eb.png)

After:
![jiren github io filter js stream html--after](https://cloud.githubusercontent.com/assets/3154126/4324766/bfe76534-3f5d-11e4-849f-96124128cffd.png)

Tested for various devices on emulator.Works fine..
I don't think an overflow-y is needed in the first place (atleast for this demo)..but let's just keep it as auto if at all needed.