Added small sample file

sample.potrero

@@ -0,0 +1,23 @@
+colors
+  1: @{colors/hue}
+
+  hue
+    1-2: red
+    3-4: green
+    5-6: blue
+    7-8: @{colors/shade} @{self}
+
+  shade
+    1: bright
+    2: dark
+
+thirty-three
+  11: one
+  12: two
+  13: three
+  21: une
+  22: deux
+  23: trois
+  31: un
+  32: du
+  33: tri