Update dependency versions to latest version

[TimvdLippe]

To make sure this implement can be cleanly installed in a Polymer 2 application,
use the latest stable versions of most of the elements.

[notwaldorf]

@ebidel@e111077 halp, should this go in? who's in charge? 👮

[ebidel]

I'm out of the loop when it comes to Polymer 2.

I've never seen the form #1 - 2. Is that something we want? IOW, is this element going to work with 2.0 without any changes?

[e111077]

@ebidel this PR is attempting to merge into the 2.0-preview branch which has already been updated to work in 2.0.

For the versioning, that's what we've been using for our 2.0 elements ¯\_(ツ)_/¯

[e111077]

Merging into 2.0-preview. It also seems as if @samuelli has been maintaining the branch. Can he be made member / collaborator please?

[joemarini]

When will these changes be updated into webcomponents.org?

[e111077]

I believe these changes do not reflect until it is merged into master ...and possibly released?

[samuelli]

Each release will show up on webcomponents.org