iOS 11 losing styles after typing 1 character

[diegoreymendez]

When using Aztec in iOS 11, styles are being lost after typing just 1 character.

How to test:

1. Open the empty editor.
2. Type a regular first line.
3. Press enter
4. Enable any style.
5. Start typing.

Expected behavior: the full line should have the selected style.
Current behavior: after the first character is entered, the style is removed.

[diegoreymendez]

Reported as a UITextView issue to Apple (Apple ref 34546954).

I've also created an example minimal project demonstrating this issue is not caused by our code.

[jleandroperez]

Closed via #726