Added formula for unafold

unafold is an extremely popular tool for computing secondary structures
of nucleic acids, and it's a standard part of the bioinformatics
repertoire.

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

Formula/unafold.rb

@@ -0,0 +1,17 @@
+require 'formula'
+
+class Unafold <Formula
+  url 'http://dinamelt.bioinfo.rpi.edu/download/unafold-3.8.tar.gz'
+  homepage 'http://dinamelt.bioinfo.rpi.edu/unafold/'
+  md5 'c1d473c1c4685b7ded51979d8fe4ce0b'
+
+  depends_on 'gd'
+  depends_on 'gnuplot'
+
+  def install
+    system "./configure", "--disable-debug", "--disable-dependency-tracking",
+                          "--prefix=#{prefix}"
+    system "make"
+    system "make install"
+  end
+end