Allow source to be a json, so it can be provided from Elm

[JordyMoos]

I would like to provide the suggestions from Elm but i can not bind a object to sources or call the suggestions method. Therefor it would be nice if i could provide the suggestions to the paper-autocomplete-suggestions one way or the other.

Solutions i was thinking about, which works from elm are:

1. Json encode the suggestions and provice a json as the source/suggestions value.

<paper-autocomplete-suggestions source="[{\"text\":\"First\",\"value\":\"First\"},{\"text\":\"Second\",\"value\":\"Second\"},{\"text\":\"Third\",\"value\":\"Third\"}]" for="searchInput" ></paper-autocomplete-suggestions>

2. Provide the data as sub elements (dunno if that is common in web components)

<paper-autocomplete-suggestions>
    <paper-suggestion text="First" value="First"></paper-suggestion>
    <paper-suggestion text="Second" value="Second"></paper-suggestion>
    <paper-suggestion text="Third" value="Third"></paper-suggestion>
</<paper-autocomplete-suggestions>

Cheers