Unit test to detect issue in 8d14efe for #126 that causes aggressive parenthesis removal, functional differences

Adds a unit test to test for aggressive parenthesis removal introduced in 8d14efe for #126 that causes functional changes.

In WordPress, we had this code (excerpted):

`'style="width: '+( 10 + parseInt(f) )+'px"'`

It used to minify like this:

`'style="width: '+(10+parseInt(f))+'px"'`

But in 2.4.1 it minifies as:

`'style="width: 10'+parseInt(f)+'px"'` (functionally different).

A fix for this is above my JS pay grade, but here's a unit test that catches the issue.