bower update with #2.0-preview fails due to missing polymer branch

[Tom Kay]

app-route 2.0-preview depends on polymer branch 2.0-data-updates, but that branch was deleted when Polymer/polymer#4221 was merged.

A PR to update dependency back to 2.0-preview is here #169

[Tom Kay]

@e111077 I saw you originally specified the data updates branch here 57f5868. Would you mind taking a look at this PR please?

[Elliott Marquez]

I flubbed the commit message but here it is dafcc0a