Added formula for Gwyddion

Gwyddion is a modular program for SPM (scanning probe microscopy) data
visualization and analysis.

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

Formula/gwyddion.rb

@@ -0,0 +1,19 @@
+require 'formula'
+
+class Gwyddion <Formula
+  url 'http://downloads.sourceforge.net/project/gwyddion/gwyddion/2.21/gwyddion-2.21.tar.bz2'
+  homepage 'http://gwyddion.net/'
+  md5 '7330a22460743c9da8dceec03f7924e9'
+
+  depends_on 'gtk+'
+  depends_on 'libxml2'
+  depends_on 'fftw'
+  depends_on 'gtkglext'
+
+  def install
+    system "./configure", "--disable-debug", "--disable-dependency-tracking",
+                          "--disable-desktop-file-update",
+                          "--prefix=#{prefix}"
+    system "make install"
+  end
+end