Use only *.styl file if an entity has multiple files (close enb#73)

techs/css-stylus.js

@@ -34,19 +34,30 @@ module.exports = require('enb/lib/build-flow').create()
         var node = this.node,
             filename = node.resolvePath(path.basename(this._target)),
             defer = vow.defer(),
+            styl = {},
             css, renderer;
 
-        css = sourceFiles.map(function (file) {
-            var url = node.relativePath(file.fullname);
-
-            if (file.name.indexOf('.styl') !== -1) {
-                return '/* ' + url + ':begin */\n' +
-                    '@import "' + url + '";\n' +
-                    '/* ' + url + ':end */\n';
-            } else {
-                return '@import "' + url + '";';
+        sourceFiles.forEach(function (file) {
+            if (isStylFile(file.name)) {
+                styl[file.name] = true;
             }
-        }).join('\n');
+        });
+
+        css = sourceFiles
+            .filter(function (file) {
+                return isStylFile(file.name) || !styl[file.name.slice(0, -3) + 'styl'];
+            })
+            .map(function (file) {
+                var url = node.relativePath(file.fullname);
+
+                if (isStylFile(file.name)) {
+                    return '/* ' + url + ':begin */\n' +
+                        '@import "' + url + '";\n' +
+                        '/* ' + url + ':end */\n';
+                } else {
+                    return '@import "' + url + '";';
+                }
+            }).join('\n');
 
         renderer = stylus(css, {
                 compress: this._compress,
@@ -98,3 +109,7 @@ module.exports = require('enb/lib/build-flow').create()
         }
     })
     .createTech();
+
+function isStylFile (name) {
+    return name.substr(-5) === '.styl';
+}