Adjust the definition divs if the word is too far to the left or the right.
Adjust the definition divs if the word is too far to the left or the right.

Summary:
Follows up from the D36744 diff where I created the definition widget. The problem was that if the word to be defined was too far to the left or the right, the definition div would go off the page. So, I had to position the div accordingly after the elements had rendered.
{F741215}

{F741214}

{F741213}

Test Plan:
 - Create a question with 3 definition widgets: one at the start of the line, one in the middle, and one at the end.
 - Verify that the definition boxes are all completely visible on the page.
 - Try adding a few characters before or after each word and refresh the page.
 - Verify that the definition boxes are all still visible and intuitive.
 - Try changing the length of the words to be defined and refresh the page.
 - Verify that the definition boxes are in the expected places.

Reviewers: emily

Reviewed By: emily

Subscribers: jared

Differential Revision: https://phabricator.khanacademy.org/D36817

ariabuckles/perseus,ariabuckles/perseus,ariabuckles/perseus,ariabuckles/perseus,learningequality/perseus,learningequality/perseus