copy&paste from gmail using IE11 adds junk

[benbro]

[Describe the issue]
When I copy a message from gmail using IE11 to quill it adds junk before the actual message text.
It doesn't happen when I copy from gmail using Chrome.
I don't see the junk when pasting in notepad, notepad++ or in gmail.
I'm not sure if it's an actual issue so feel free to close it if it's something specific to old IE.

Steps for Reproduction

1. Visit http://quilljs.com/
2. Open gmail in IE11 on Windows 7
3. Compose a new mail, type 'Test', select all (ctrl+a), and copy (ctrl+c).
4. Paste the text in quill.

Expected behavior: [expected]
See only the word 'Test' in quill.

Actual behavior: [actual]
Several lines of text are added above the actual message. It starts with:

Inbox - [email protected] - Gmail     // <![CDATA[ var GM_START_TIME=(new Date).getTime();var GM_SUPPORTED_IE_VERSION="9.0";var
...

Platforms: [ex. Chrome 48 on Mac 10.11]
Chrome 52 on Windows 7.
(copy from gmail using IE11 on Windows 7).

Version: [version]
1.0.0-rc2

[benbro]

Please note, I need to copy the text with IE11 to reproduce but Quill adds the CDATA part when pasting in all browsers (Chrome, Firefox). That's not an IE11 only issue.

I can't reproduce when I copy from a simple textarea,
http://codepen.io/anon/pen/PzAVdA

I can't reproduce when I copy from a simple contenteditable
http://codepen.io/anon/pen/rLEPqy

I saw a similar issue when I copy text from the medium.js editor with IE11.
Quill tries to load arbitrary css files. Is this a security issue?

NetworkError: 404 Not Found - http://s.codepen.io/quill/medium.css
NetworkError: 404 Not Found - http://s.codepen.io/quill/fullembedgrid/prism.css
NetworkError: 404 Not Found - http://s.codepen.io/quill/fullembedgrid/docs.css

Steps for Reproduction

1. Use IE11 and visit http://jakiestfu.github.io/Medium.js/docs/
2. Scroll down to the demos. Type 'abc', select the text and copy (ctrl+c)
3. Use Chrome or Firefox and visit http://quilljs.com/playground/
4. Paste the text.

[benbro]

I also see the same issue when I copy with Edge on Windows 10:
Microsoft Edge 38.14393.0.0
Microsoft EdgeHTML 14.14393