This version is compatible with Polymer 1 and Polymer 2, but required
for Polymer 2.
Elements that were formerly
<input is="iron-input>
are now
<iron-input>
<input>
</iron-input>
There are a few scenarios in which inputs were not using two way data
binding, which is the reason for using iron-input, and those have been
modified back to a native input.
With the updated iron-input to access the native input, there is an
'inputElement' getter function, which is used heavily in this update.
Also of note, in many tests, it is required to wrap Polymer.Base.async,
which is necessary because the mutation observer is async:
https://github.com/PolymerElements/iron-input/blob/master/test/iron-input.html
Also modifies polylint_test to explicitly ignore bower_components.
Change-Id: I75f7fa1bb0c00837f631f6e1043e15a3270b9bce
37636a6256