fixed Bounce ease
UITextInstance was breaking if you changed the scale and then updated the text. The child text sprites would inherit the UITextInstance scale (which causes them to have the wrong scale).
Now, when you update the text, it first reverts the scale of the UITextInstance to (1,1,z), then updates the text, and finally restores the scale back to the original amount.

This way you can scale UITextInstance via the scale or localScale property, which is more performant than scaling via .textScale (which causes  a complete text redraw).

Also fixed a bug where changing the align mode or vertical align mode if you have a zero length string would cause a crash.
Merge pull request #131 from tayl0r/p31-master

fixed Bounce ease + UITextInstance scaling
added UISlice9 courtesy of David O'Donoghue (ODD Games)
updated contributors
Add support for Linux
Merge pull request #143 from mortennobel/master

Add support for Linux