added poll placeholder sizes to the model and used them in <img /> tag as its attributes
removed sizes from scss because we use them in <img /> tag now
renamed the method and one variable
removed part of code which was not executed at all -- it was a wikia poll placeholder which now is rendered by WikiaPoll hook method
change after code review: it is better in performance terms not to create stdObject just to return width and height values; removed getRtePlaceholderSize() and added two small getters instead
Merge pull request #689 from Wikia/consumer-spirnt38-bugid-101586

Fix hover state of Wikia Poll placeholder in RTE