update README file

Author: Todd Whiteman

README.md

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+# Komodo Side-By-Side Diffs
+
+Provides the ability to use side-by-side diffs inside of Komodo. You get to
+choose which diff style you want on demand (contextual or side by side), simply
+choose the style you want inside of the Komodo diff dialog.
+
+## Screenshot
+
+![Screenshot](screenshots/sbsdiffs.png)
+
+## Download
+
+You can use Komodo's "Tools > Add-ons" dialog to install the add-on, since the
+add-on is published on the Komodo community extension list:
+http://community.activestate.com/xpi/side-side-diff
+
+## Building from source
+
+  koext build --unjarred
+