https for cgiar source, fixes graphhopper#2255

Author: karussell

core/src/main/java/com/graphhopper/reader/dem/CGIARProvider.java

@@ -54,7 +54,7 @@ public CGIARProvider() {
 
     public CGIARProvider(String cacheDir) {
         // Alternative URLs for the CGIAR data can be found in #346
-        super("http://srtm.csi.cgiar.org/wp-content/uploads/files/srtm_5x5/TIFF/",
+        super("https://srtm.csi.cgiar.org/wp-content/uploads/files/srtm_5x5/TIFF/",
                 cacheDir.isEmpty() ? "/tmp/cgiar" : cacheDir,
                 "GraphHopper CGIARReader",
                 6000, 6000,