Update grid.base.js

Added namespace for mouseup. Required for cleaning up the event when the grid is getting destroyed. Added additional param, id for namespace since a page can have multiple grid and destroying of one grid should not clear namespace for others.
Update grid.custom.js

Unbinding of mouseup event with proper namespace.
Update grid.base.js

Set res to null. Chrome heap profiler show "res" as unclaimed cause it still see the reference existing at this function.
Merge pull request #496 from kunalkumar/master

Namespace for Mouseup event and Unbinding Call