Displaying mobbr button in question lists

This should get the job done without requiring the Q2A core to be modified as requested here https://github.com/q2a/question2answer/issues/157.

The branch is actually untested as I don't know anything about mobbr. However, I haven't made any change in the logic so it should work the same as before.

It is important to note that the button has to be customized per theme, as I explained in the linked ticket. In case of the SnowFlat (Q2A v1.7) theme it seems to be working without any code change:

![mobbr1](https://cloud.githubusercontent.com/assets/1449790/5294260/1d7f1108-7b61-11e4-974b-3acaff1da411.png)

In case of the Snow (Q2A v1.6) theme I had to add this CSS fix:
```css
.qa-q-item-main {
	width: 440px;
}
```

![mobbr-2](https://cloud.githubusercontent.com/assets/1449790/5294269/491a38ba-7b61-11e4-8aa0-ef4594788436.png)