Nested text symbol

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### Feature request

Not sure if this is user error or a feature request. I have a button with nested text as a symbol. As a result, the button size doesn't change to account for text increase. 


https://www.dropbox.com/s/vzew5kkdzm7ofs3/paddy-test-button.sketch?dl=0


![image](https://user-images.githubusercontent.com/37604381/37691842-039cbd10-2c72-11e8-9984-8aa3f80f5e0a.png)


