* Added Grid class to hold the traverseGrid method
* Added Optional to Tile and GameManager to look for merging nullable tiles
* Provided default styling to grid
* Added Grid class to hold the traverseGrid method
* Added Optional to Tile and GameManager to look for merging nullable tiles
* Provided default styling to grid
* Refactoring in GameManager
* Refactoring in GameManager
* Renamed Grid to GridOperator, since it's a funcional not a Node.
* Refactoring in GameManager
* Renamed Grid to GridOperator, since it's a funcional not a Node.
* More refactoring in GameManager, extending the use of Optional<Tile>
* Extended the use of GridOperator to SessionManager
* More refactoring in GameManager, reordering methods
* Added javadoc to GameManager
Merge pull request #20 from jperedadnr/master

* Added Grid class to hold the traverseGrid method