REXML is dead. Long live Nokogiri.

Modify Maruku to use Nokogiri instead of REXML.
Produces a 3-fold speedup in the #to_html method.

vendor/plugins/maruku/spec/block_docs/inline_html2.md

@@ -0,0 +1,21 @@
+
+*** Parameters: ***
+{}
+*** Markdown input: ***
+<div markdown="1">Test **bold**</div>
+<p markdown="1">Test **bold**</p>
+*** Output of inspect ***
+md_el(:document,[
+	md_html("<div markdown=\"1\">Test **bold**</div>"),
+	md_html("<p markdown=\"1\">Test **bold**</p>")
+],{},[])
+*** Output of to_html ***
+<div>
+<p>Test <strong>bold</strong></p>
+</div><p>Test <strong>bold</strong></p>
+*** Output of to_latex ***
+
+*** Output of to_md ***
+
+*** Output of to_s ***
+