Merge pull request #1 from mwoc/master

Memory leak fix
Accepting observable arrays as data sources
Added first test
Added tests to validate basic consistency
Testing that the correct tiles are rendered with the correct information
Testing rendering of tiles when moving the viewport
Testing added to the end of the list
Testing that there are no gaps or overlappnig between tiles
More testing and improving the examples
Testing insertion in the middle of the viewport
Renamed viewPort to viewport