change to use a hosted dep on polymer_elements
Merge pull request #453 from dart-lang/polymer_elements

change to use a hosted dep on polymer_elements
Refresh folders when the focus is back on the app window
Remove dependencies on the unused polymer_elements
Merge pull request #460 from ussuri/fix-polymer-dependencies

Remove dependencies on the unused polymer_elements
Locked range of Polymer version

Couldn't get pub to download 0.9.2+4 for ide/ with 'polymer: any', even though it did so for widgets/.
Merge pull request #461 from ussuri/fix-polymer-dependencies

Locked range of Polymer version
Added file deletion feature to the mock file system. Added a unit test for Workspace.checkForChange()
Added TODOs and improved comments. checkForChange() -> refresh().
Merge pull request #458 from dinhviethoa/302-refresh-folders

Refresh workspace when the focus is back on the app window.