Use https for repositories

Author: javier-godoy

pom.xml

@@ -51,11 +51,11 @@
     <repositories>
         <repository>
             <id>Vaadin Directory</id>
-            <url>http://maven.vaadin.com/vaadin-addons</url>
+            <url>https://maven.vaadin.com/vaadin-addons</url>
         </repository>
         <repository>
             <id>Vaadin prereleases</id>
-            <url>http://maven.vaadin.com/vaadin-prereleases</url>
+            <url>https://maven.vaadin.com/vaadin-prereleases</url>
         </repository>
         <!-- The bintray repository contain webjars immediately after generation. If the webjar is available
              in Maven central, you do not need this repository -->