Text is entered above code block in Firefox and IE

[benbro]

[Describe the issue]
With Chrome the cursor is on the top of the code block and when typing jump to the middle.
On Firefox and IE the text is above the code block.

Steps for Reproduction

1. Visit http://beta.quilljs.com/docs/formats/
2. Focus the editor
3. Click on the code block button
4. Type something

Expected behavior: [expected]
Text should be inside the code block.

Actual behavior: [actual]
Text is above the code block

Platforms:
Firefox 47, IE 11, Chrome 51 on Windows 7

Version: [version]
1.0-beta.9