Document backslash-escapes in Sass.

lib/sass.rb

@@ -253,6 +253,22 @@ $LOAD_PATH << dir unless $LOAD_PATH.include?(dir)
 #     font-size: 30em;
 #     font-weight: bold; }
 #
+# === Rule Escaping
+#
+# In case, for whatever reason, you need to write a rule
+# that begins with a Sass-meaningful character,
+# you can escape it with a backslash (<tt>\</tt>).
+# For example:
+#
+#  #main
+#    \+div
+#      clear: both
+#
+# is compiled to:
+#
+#  #main +div {
+#    clear: both; }
+#
 # == Constants
 #
 # Sass has support for setting document-wide constants.