NextDouble instead of nextInt. (#46)

Author: Kevin Hellemun

src/main/java/com/bunq/sdk/json/BigDecimalTypeAdapter.java

@@ -32,7 +32,7 @@ public BigDecimal read(JsonReader input) throws IOException {
     JsonToken type = input.peek();
 
     if (type == JsonToken.NUMBER) {
-      return new BigDecimal(input.nextInt());
+      return new BigDecimal(input.nextDouble());
     } else if (type == JsonToken.STRING) {
       return new BigDecimal(input.nextString());
     } else {