Renamed blocks to closures

## What? Why?
In Swift blocks are treated as Closures instead

## What should be tested?
Everything works and tests are passing after the renaming

## Related tasks? 
**Related issue** https://github.com/SugarRecord/SugarRecord/issues/11

![image](http://media.giphy.com/media/fdiWBMyTEAhjy/giphy.gif)