Merge pull request #9 from ecruciani/master

Add .gitignore with Intellij files
Added two new attributes scroll-top-position and scroll-left-position that let set programmatically the middle center area scrolling position.
Completed documentation
Added 2 test files
Merge branch 'master' of https://github.com/gdepourtales/ng-cells

# By eric
# Via Guy de Pourtalès (1) and eric (1)
* 'master' of https://github.com/gdepourtales/ng-cells:
  Add .gitignore with Intellij files