Merge pull request #6 from panovitch/custom-header-override-defaults

Custom headers now override the default ones (bunq#141)

src/main/java/com/bunq/sdk/http/ApiClient.java

@@ -243,7 +243,7 @@ private void setDefaultHeaders(BunqRequestBuilder httpEntity) {
      */
     private void setCustomHeaders(Request.Builder requestBuilder, Map<String, String> customHeaders) {
         for (Map.Entry<String, String> entry : customHeaders.entrySet()) {
-            requestBuilder.addHeader(entry.getKey(), entry.getValue());
+            requestBuilder.header(entry.getKey(), entry.getValue());
         }
     }