Remove unnecessary "match anything" test that caused excessive run time on some mixed content

Update HTML5 structural tags test to also verify correctness this regexp and the previous one.

Signed-off-by: unwiredben <combee@techwood.org>

src/showdown.js

@@ -259,13 +259,13 @@ var _HashHTMLBlocks = function(text) {
 			\b					// word break
 								// attacklab: hack around khtml/pcre bug...
 			[^\r]*?				// any number of lines, minimally matching
-			.*</\2>				// the matching end tag
+			</\2>				// the matching end tag
 			[ \t]*				// trailing spaces/tabs
 			(?=\n+)				// followed by a newline
 		)						// attacklab: there are sentinel newlines at end of document
 		/gm,function(){...}};
 	*/
-	text = text.replace(/^(<(p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|script|noscript|form|fieldset|iframe|math|style|section|header|footer|nav|article|aside)\b[^\r]*?.*<\/\2>[ \t]*(?=\n+)\n)/gm,hashElement);
+	text = text.replace(/^(<(p|div|h[1-6]|blockquote|pre|table|dl|ol|ul|script|noscript|form|fieldset|iframe|math|style|section|header|footer|nav|article|aside)\b[^\r]*?<\/\2>[ \t]*(?=\n+)\n)/gm,hashElement);
 
 	// Special case just for <hr />. It was easier to make a special case than
 	// to make the other regex more complicated.

test/cases/html5-strutural-tags.html

@@ -9,8 +9,11 @@
 
 <nav>navigation</nav>
 
-<article>read me</article>
+<article>read
+me</article>
 
-<aside>ignore me</aside>
+<aside>
+ignore me
+</aside>
 
 <p>the end</p>

test/cases/html5-strutural-tags.md

@@ -5,7 +5,10 @@ These HTML5 tags should pass through just fine.
 <header>head</header>
 <footer>footsies</footer>
 <nav>navigation</nav>
-<article>read me</article>
-<aside>ignore me</aside>
+<article>read
+me</article>
+<aside>
+ignore me
+</aside>
 
 the end