Pasting text that contains a newline throws an error

[YoranBrondsema]

I think this is a regression introduced by #459. Inserting text with newlines inside a list works, as per the fix. However, inserting text with newlines outside of a list, for instance in an empty Mobiledoc instance, fails.

[bantic]

Darn, I knew that fix yesterday seemed too simple.
I will address this today and expand the test coverage for the post-insertion tests. Thanks for reporting!

[bantic]

released in v0.10.7