Adds visual tests that cover whitespace behavior in text mode

test/visual.html

diff --git a/test/visual.html b/test/visual.html
index a2207d1..1f77a3c 100644
--- a/test/visual.html
+++ b/test/visual.html
@@ -282,6 +282,12 @@
 

 <p>Should wrap anything you type in '&lt;&gt;': <span id="wrap-typing">1+2+3</span></p>

 

+<h3>Text mode</h3>

+

+<p>Spaces at the beginning and end of text mode blocks should be visible: <span class="mathquill-static-math">1\text{ And }2</span></p>

+

+<p>Mutiple consecutive spaces in the middle of a text mode block should not collapse into one space: <span class="mathquill-static-math">\text{three   spaces}</span></p>

+

 </div>

 <script type="text/javascript">

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