Fix bug preventing import of files with dots in their name

Closes #11

index.js

@@ -42,7 +42,7 @@ var importOnce = function importOnce(data, done) {
  * they leave off the partial prefix and the suffix.
  * This code creates the possible extensions, whether it is a partial
  * and whether it is a directory index file having those
- * same possible variations. If the import contains an extension,
+ * same possible variations. If the import contains a valid extension,
  * then it is left alone.
  *
 **/
@@ -51,7 +51,7 @@ var getFileNames = function getFileNames(abstractName) {
       directory,
       basename;
 
-  if (path.extname(abstractName)) {
+  if ([ '.scss', '.sass', '.css', '.json', '.yaml' ].indexOf(path.extname(abstractName)) !== -1) {
     names.push(abstractName);
   }
   else {

test/css/import-with-dot.css

@@ -0,0 +1,2 @@
+.some-class-in-dotted-file {
+  color: blue; }

test/main.js

@@ -267,4 +267,27 @@ describe('import-once', function () {
       done();
     });
   });
+
+  it('should import a file with dots in its name', function(done) {
+    var file = filePath('import-with-dot.scss'),
+        expectedIncludes = [
+          file,
+          filePath('file.with.dot.scss')
+        ];
+
+    sass.render({
+      'file': file,
+      'importer': importer
+    }, function(err, result) {
+      if (err) {
+        throw err;
+      }
+      should.exist(result);
+      result.stats.includedFiles.should.eql(expectedIncludes);
+      String(result.css).should.equal(
+        fs.readFileSync(path.join(__dirname, 'css/import-with-dot.css'), 'utf8')
+      );
+      done();
+    });
+  });
 });

test/sass/file.with.dot.scss

@@ -0,0 +1,3 @@
+.some-class-in-dotted-file {
+  color: blue;
+}

test/sass/import-with-dot.scss

@@ -0,0 +1 @@
+@import "file.with.dot";