Use HTTPS instead of HTTP to resolve dependencies

This fixes a security vulnerability in this project where the `pom.xml`
files were configuring Maven to resolve dependencies over HTTP instead of
HTTPS.

Signed-off-by: Jonathan Leitschuh <Jonathan.Leitschuh@gmail.com>
diff --git a/servlet-vaadin-v10/pom.xml b/servlet-vaadin-v10/pom.xml
index bc78a9a..38964d8 100644
--- a/servlet-vaadin-v10/pom.xml
+++ b/servlet-vaadin-v10/pom.xml
@@ -47,13 +47,13 @@
     <!--Releases-->
     <repository>
       <id>vaadin-addons</id>
-      <url>http://maven.vaadin.com/vaadin-addons</url>
+      <url>https://maven.vaadin.com/vaadin-addons</url>
     </repository>
 
     <!--Pre-Releases-->
     <repository>
       <id>vaadin-prereleases</id>
-      <url>http://maven.vaadin.com/vaadin-prereleases</url>
+      <url>https://maven.vaadin.com/vaadin-prereleases</url>
     </repository>
   </repositories>
 
diff --git a/servlet-vaadin-vxx/pom.xml b/servlet-vaadin-vxx/pom.xml
index 6135454..710675b 100644
--- a/servlet-vaadin-vxx/pom.xml
+++ b/servlet-vaadin-vxx/pom.xml
@@ -28,13 +28,13 @@
     <!--Releases-->
     <repository>
       <id>vaadin-addons</id>
-      <url>http://maven.vaadin.com/vaadin-addons</url>
+      <url>https://maven.vaadin.com/vaadin-addons</url>
     </repository>
 
     <!--Pre-Releases-->
     <repository>
       <id>vaadin-prereleases</id>
-      <url>http://maven.vaadin.com/vaadin-prereleases</url>
+      <url>https://maven.vaadin.com/vaadin-prereleases</url>
     </repository>
   </repositories>