Strip out './' when looking up relative @imports.

This was causing JRuby to choke on templates in a jar importing each other.

Relevant Stack Overflow question: http://stackoverflow.com/questions/8236327/getting-file-not-found-error-running-sass-and-compass-as-jar-in-ant

Closes #583

doc-src/SASS_CHANGELOG.md

@@ -3,6 +3,11 @@
 * Table of contents
 {:toc}
 
+## 3.2.4 (Unreleased)
+
+* Fix imports from `.jar` files in JRuby. Thanks to [Alex
+  Hvostov](https://github.com/argv-minus-one).
+
 ## 3.2.3
 
 * `sass --watch` no longer crashs when a file in a watched directory is deleted.

lib/sass/importers/filesystem.rb

@@ -91,8 +91,14 @@ def possible_files(name)
         sorted_exts = extensions.sort
         syntax = extensions[extname]
 
-        return [["#{dirname}/{_,}#{basename}.#{extensions.invert[syntax]}", syntax]] if syntax
-        sorted_exts.map {|ext, syn| ["#{dirname}/{_,}#{basename}.#{ext}", syn]}
+        if syntax
+          ret = [["#{dirname}/{_,}#{basename}.#{extensions.invert[syntax]}", syntax]]
+        else
+          ret = sorted_exts.map {|ext, syn| ["#{dirname}/{_,}#{basename}.#{ext}", syn]}
+        end
+
+        # JRuby chokes when trying to import files from JARs when the path starts with './'.
+        ret.map {|f, s| [f.sub(%r{^\./}, ''), s]}
       end
 
       def escape_glob_characters(name)
@@ -118,7 +124,7 @@ def find_real_file(dir, name, options)
         end
         found = Sass::Util.flatten(found, 1)
         return if found.empty?
-  
+
         if found.size > 1 && !@same_name_warnings.include?(found.first.first)
           found.each {|(f, _)| @same_name_warnings << f}
           relative_to = Pathname.new(dir)