Use absolute URL for Dependency Mechanism link (#140)

The relative link starting with / is being ignored and the browser tries to open the fowlling link that does not exist:
https://maven.apache.org/plugins/maven-dependency-plugin/guides/introduction/introduction-to-dependency-mechanism.html

Also update http links to https in other pages.
diff --git a/src/site/apt/examples/copying-project-dependencies.apt.vm b/src/site/apt/examples/copying-project-dependencies.apt.vm
index 1f96a1c..012dd1c 100644
--- a/src/site/apt/examples/copying-project-dependencies.apt.vm
+++ b/src/site/apt/examples/copying-project-dependencies.apt.vm
@@ -63,7 +63,7 @@
 
 * Excluding transitive dependencies
 
-   As mentioned, {{{http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html}transitive dependencies}} are copied by default. However, they
+   As mentioned, {{{https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html}transitive dependencies}} are copied by default. However, they
    can also be excluded by setting the <<<excludeTransitive>>> property to
    <<true>>.
 
diff --git a/src/site/apt/index.apt.vm b/src/site/apt/index.apt.vm
index c43e4bf..3e4b193 100644
--- a/src/site/apt/index.apt.vm
+++ b/src/site/apt/index.apt.vm
@@ -150,6 +150,6 @@
   Here is a link that provides more reference regarding dependencies
   (i.e. dependency management, transitive dependencies).
 
-  * {{{http://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html}Dependency Mechanism}}
+  * {{{https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html}Dependency Mechanism}}
 
   []
diff --git a/src/site/site.xml b/src/site/site.xml
index afec97a..c954fc1 100644
--- a/src/site/site.xml
+++ b/src/site/site.xml
@@ -45,7 +45,7 @@
       <item name="Purging local repository dependencies" href="examples/purging-local-repository.html"/>
     </menu>
     <menu name="Resources">
-      <item name="Dependency Mechanism" href="/guides/introduction/introduction-to-dependency-mechanism.html"/>
+      <item name="Dependency Mechanism" href="https://maven.apache.org/guides/introduction/introduction-to-dependency-mechanism.html"/>
     </menu>
   </body>
 </project>