Nice formatting of code blocks

code blocks are put into
```scala
   val info = "scala code goes here"
   //example
   require(y > 0, "y must be positive")
```
this adds nice formatting, and simplify reading

Compare original with this: https://github.com/dmakhno/progfun-wiki/blob/51d16a3b50586fea400bb17a74750ee369058b67/CheatSheet.md