feat(gridster): enable resize of gridster container

Enable the resizing of the container for the gridster. Previously, the directive used to
listen to the windows `resize` event only.
Fix for the generic resize event. New width/height values are now kept separately from
the actual width/height config, that can be a string (auto or match).
Add test methods for the new resize parameters.
Implement a protractor test to check for the test behavior.
Generate dist files.
Update `index.html` to reflect new changes.
Update `README.md` with import information.
Add .idea folder to gitignore files.

Close #52.
Merge pull request #53 from frapontillo/feature/resize-element

feat(gridster): enable resize of gridster container