Fix internal links in the metrics chapter

Author: dicortazar

SUMMARY.md

@@ -18,15 +18,15 @@
   * [Goal-Question-Metric Approach](measuring/gqm.md)
   * [Strategy](measuring/strategy.md)
   * [Examples of Interest](measuring/metrics.md)
-    * [Mentorship and helping Newcomers](measuring/metrics.md#mentorships)
-    * [Development Cycle](measuring/metrics.md#development)
-    * [Contributors Funnel](measuring/metrics.md#funnel)
+    * [Mentorship and helping Newcomers](measuring/metrics.md#mentorships-and-helping-newcomers)
+    * [Development Cycle](measuring/metrics.md#development-cycle)
+    * [Contributors Funnel](measuring/metrics.md#contributors-funnel)
     * [Engagement](measuring/metrics.md#engagement)
-    * [Break Silos](measuring/metrics.md#silos)
-    * [Spreading the Knowledge](measuring/metrics.md#knowledge)
-    * [Middle Management Cultural Change](measuring/metrics.md#cultural_change)
+    * [Break Silos](measuring/metrics.md#break-silos)
+    * [Spreading the Knowledge](measuring/metrics.md#spreading-the-knowledge)
+    * [Middle Management Cultural Change](measuring/metrics.md#middle-management-cultural-change)
     * [Scalability](measuring/metrics.md#scalability)
-    * [Keep great Developers in House](measuring/metrics.md#happy_devs)
-    * [Allow Innovation in Detail](measuring/metrics.md#innovation)
+    * [Keep great Developers in House](measuring/metrics.md#keep-great-developers-in-house)
+    * [Allow Innovation in Detail](measuring/metrics.md#allow-innovation-in-detail)
   * [References](measuring/references.md)
   * [Authors and Reviewers](measuring/authors.md)