Fix broken markdown in docs (#306).

lib/src/rules/empty_constructor_bodies.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library linter.src.rules.empty_constructor_bodies;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/ast/visitor.dart';
 import 'package:analyzer/src/dart/ast/token.dart';
 import 'package:linter/src/linter.dart';
 
 const desc = 'Use `;` instead of `{}` for empty constructor bodies.';
 
 const details = '''
-From the [style guide] (https://www.dartlang.org/articles/style-guide/):
+From the [style guide](https://www.dartlang.org/articles/style-guide/):
 
 **DO** use ; instead of {} for empty constructor bodies.
 
 In Dart, a constructor with an empty body can be terminated with just a
 semicolon. This is required for const constructors. For consistency and
 brevity, other constructors should also do this.
 
 **GOOD:**
 
 ```
@@ skipping 34 matching lines @@
     if (node.body is BlockFunctionBody) {
       Block block = (node.body as BlockFunctionBody).block;
       if (block.statements.length == 0) {
         if (block.endToken is! TokenWithComment) {
           rule.reportLint(block);
         }
       }
     }
   }
 }