Add a note in the readme to avoid sprockets directives.

Author: chriseppstein

README.markdown

@@ -21,6 +21,14 @@ properties that will be passed to Sass.
       config.sass.syntax = :nested
     end
 
+### Important Note
+
+Sprockets provides some directives that are placed inside of comments called `require`, `require_tree`, and
+`require_self`. **DO NOT USE THEM IN YOUR SASS/SCSS FILES.** They are very primitive and
+do not work well with Sass files. Instead, use Sass's native `@import`
+directive which `sass-rails` has customized to integrate with the
+conventions of your rails projects.
+
 ### Options
 
 The [list of supported options](http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#options) can be found on the Sass Website with the following  caveats:
@@ -67,4 +75,4 @@ The [list of supported options](http://sass-lang.com/docs/yardoc/file.SASS_REFER
     $ bundle install
     $ bundle exec rake test
 
-If you need to test against local gems, use Bundler's gem :path option in the Gemfile and also edit `test/support/test_helper.rb` and tell the tests where the gem is checked out.
+If you need to test against local gems, use Bundler's gem :path option in the Gemfile and also edit `test/support/test_helper.rb` and tell the tests where the gem is checked out.