Fix readme extension

Author: Gareth R

README.markdown

@@ -0,0 +1,6 @@
+A simple GUI for carrying out pre-activity checks.
+Checks are read from a simple text file called checklist.txt, one item to a line.
+C style single line comments are supported.  
+The !Launch program directive will display a button to launch program.
+The return key will advance to the next item. Any other key will focus the notes field.
+!(https://github.com/downloads/blutack/checkov/screenshot.png)