Update Default.png
Change background image of navigation bar

* Set toolbarTintColor of webViewController
Customize back bar button item
Change layout of feed item cells
Remove sections of date in feed items list
Change layout of feed item contents
Fix title label width in feed items list
Fix IC/CI typo
Add feed link cell in feed item content view
Use imageEdgeInsets of UIButton to set image margin

* Restore the original design of backBtn
Fix distortion of back bar button item on device

* Remove imageEdgeInsets
* Provide row height from feed item cell class
Change __weak to __block
Merge pull request #7 from polydice/feature/designUserInterface

Feature/design user interface