Adjusted styles for sidebar featured team and created partial for markup separation.

Work for # 143
https://assembly.com/coderwall/wips/143

Markup and css has been adjusted to account for Featured Teams that have uploaded custom images to their Team profile:

Previous:
This is what the widget looked like previously.  Notice the avatar had negative margin which made it overlap the custom image.
![current](https://cloud.githubusercontent.com/assets/197892/3462624/7110f972-022f-11e4-87d0-11dd0ef24b44.png)



Updated:
This is what a featured team looks like with custom uploaded image:
![custom-image](https://cloud.githubusercontent.com/assets/197892/3462538/80c90f4a-022e-11e4-8547-c662ee3bcfc8.png)


No custom image:
This is what a featured team looks like without custom uploaded image:
![default-image](https://cloud.githubusercontent.com/assets/197892/3462530/677a3852-022e-11e4-9780-e4cd85a1aa13.png)