Fix delegate problem while view controller disappear.
Hide picture cell if there's no image to display in feed item content view
Stop feed parsing when feed items list is popped from navigation stack
Add an UIAutomation script to test navigation push and pop repeatedly
Move feed parser refresh from viewWillAppear to viewDidLoad
Add lines between paragraphs in feed content preview
Merge pull request #6 from polydice/feature/fixBackButtonCrashIssue

Feature/fix back button crash issue