Fix issue #144: Method retrieveStream of IPFS class has hardcoded "http"

Author: gjeanmart

src/main/java/io/ipfs/api/IPFS.java

@@ -724,7 +724,7 @@ private List<Object> getAndParseStream(String path) throws IOException {
     }
 
     private InputStream retrieveStream(String path) throws IOException {
-        URL target = new URL("http", host, port, version + path);
+        URL target = new URL(protocol, host, port, version + path);
         return IPFS.getStream(target);
     }