When readOnly is true, toolbar still works

[jgmedialtd]

When config > readOnly is set to true, toolbar can still edit the content (select the list button as an example - converts the text to list)

Steps for Reproduction

1. Initialise a quill element with the configuration readOnly = true
2. Click on the list button on the toolbar

Expected behavior:

Toolbar buttons do nothing to the content until 'contenteditable' is true

Actual behavior:

The content is converted to to a list

Platforms:

Chrome 54.0.2840.98 (64-bit), Mac

Version:

1.1.5