Update discount to 1.6.6

From [discount's website][1.6.6]:

  * version 1.6.6 repairs two defects, one in the markdown compiler and one in
  `theme`:

    1. In `theme`, I needed to take into account the source filename
       might not have an extension when I'm making the `.html` filename.
       The old behavior was to look for a dot and put the `.html` after
       that, but _I didn't check to see if there was actually a dot there_
       before appending the `.html`!

       This did not work out too well if there was no dot.

    2. In the markdown parser, I wasn't handling escapes of the
       open square bracket inside a `[]()` construct.
       So a link like
	   [foo\[and\]bar](does not work properly!)
       would not parse because
       my square bracket matcher would look for an additional `]`
       to match the `\[` inside the `[]` part.

[1.6.6]: http://www.pell.portland.or.us/~orc/Code/discount/#1.6.6

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Formula/discount.rb

@@ -1,9 +1,9 @@
 require 'formula'
 
 class Discount <Formula
-  url 'http://github.com/Orc/discount/tarball/v1.6.5'
+  url 'http://github.com/Orc/discount/tarball/v1.6.6'
   homepage 'http://www.pell.portland.or.us/~orc/Code/markdown/'
-  md5 '85824f81b67649fb466fa469da5b5262'
+  md5 'c05cb804bdf5013aea2e816e5d2233d7'
 
   def install
     system "./configure.sh", "--prefix=#{prefix}", "--mandir=#{man}", "--enable-dl-tag", "--enable-pandoc-header", "--enable-superscript", "--relaxed-emphasis", "--enable-div", "--enable-alpha-list"