Apply responsive design for Contributors graphs.

## What does this MR do?

Makes the Contributors graphs work on mobile.

## Are there points in the code the reviewer needs to double check?

That this doesn't break on any screen sizes.

## Why was this MR needed?

It used to be squished and impossible to read.

## What are the relevant issue numbers?

Fixes #18845.

## Screenshots (if relevant)

Before:

![Screen_Shot_2016-06-18_at_1.00.58_PM](/uploads/bc17df5dabed0085c8ffdca303a502a5/Screen_Shot_2016-06-18_at_1.00.58_PM.png)

After:

![Screen_Shot_2016-06-20_at_9.21.03_AM](/uploads/a0307cb255646800d0e4c8647769f7b6/Screen_Shot_2016-06-20_at_9.21.03_AM.png)

cc: @jschatz1 

See merge request !4801