Fix Guardfile

Author: fangyi-zhou

Guardfile

@@ -1,9 +1,9 @@
 require 'fileutils'
 
 guard :shell do
-  watch(%r{^.+\.(lagda)$}) do |m|
+  watch(%r{^(.+)\.lagda\.md$}) do |m|
     src = m[0]
-    out = "#{File.dirname(src).sub('src','out')}/#{File.basename(src,'.*')}.md"
+    out = "#{File.dirname(src).sub('src','out')}/#{File.basename(src,'.lagda.md')}.md"
     `make #{out}` unless File.basename(src).start_with?('.#')
   end
 end