Remove HTML4 data-* attributes, and replace with `is`

[revivek]

As of June 10, 2015, we can remove the data-* attributes that get search and replaced (data-bgcolor, data-align, etc.) to the HTML4 variants. We can use the is property. This should also fix an unlikely but still possible bug resulting from the current search and replace strategy: since we operate on the raw string, all of data-background and its cousins would be replaced. This means an HTML5 newsletter writing about how "AlignerFoo.js uses data-align to align your elements" would turn into "AlignerFoo.js uses align to align your elements."

facebook/react#140 (comment)
facebook/react#3752

To do:

• Remove data-* attributes from OyTable, OyImg, etc.
• Place is attribute before those removed data-* attributes.
• Remove current find and replacing of data-* attributes in utils/HTML4.js
• Add a test to make sure that case above doesn't occur.

[revivek]

Using is unfortunately introduced a new set of issues—adding is means that every prop is set to an attribute. So <OyImg className="foo" /> leads to <img className="foo" />, which is problematic.

Few solutions:

1. Use a whitelist for every Oy element. This means adding class, id, etc. to every element.
2. Go back to using data-* attributes, and try to decrease the likelihood of find-and-replace collisions.

Out of the two, I think #2 is more tenable and future-proof, though involves more code.