Implemented set custom activiti indicator view.
Added setInfiniteIndicatorView: method
Merge pull request #3 from nsleader/devel

Implemented the setting of a custom indicator
Clean up spacing
ARC will zero stack variable anyway
Refactor lazy initializer for indicator view
- Look for startAnimating and stopAnimating methods on indicator view
- Manually hide indicator for consistency
Move custom indicator code into class
Add instruction for custom indicators, screencasts and contributors section
Update README
Make sure indicator is initially hidden
Bump 0.5.0
Show or hide activityIndicator regardless animation methods availability
Bump 0.5.1
Add TODO