Too many Sourcegraph extensions wreck GitHub toolbar UI

Created by: ryan-blunden

https://github.com/sourcegraph/sourcegraph/blob/master/browser/src/libs/github/file_info.ts#L22

Screen Shot 2019-06-12 at 3 28 05 PM

I would break this issue into two parts:

What can we do to the extensions to make them take up less space?

Change the button text of the code-ownership extension to be a GitHub icon and the word Owners and the owners are displayed on hover in the tooltip.
Change the Sentry button to be the logo
Change the Codecov button to be the logo

Adjust styling to accommodate for button overflow.