Make default value of minsize to 100% (issue #103)

This is consistent with MathML 3 and works as desired now that percentages
are interpreted relative to the unstretched size.

spec.html

@@ -5672,7 +5672,7 @@ <h3>Operator Dictionary</h3>
         </div>
         <p>The <dfn class="abstract-op">algorithm to set the properties of an operator from its category</dfn> is as follows:</p>
         <ul class="algorithm">
-          <li>Set <code>minsize</code> to <code>1em</code>.</li>
+          <li>Set <code>minsize</code> to <code>100%</code>.</li>
           <li>Set <code>maxsize</code> to <code>∞</code>.</li>
           <li>Find the row corresponding to the specified category
             on <a href="#operator-dictionary-categories-values"></a>.