Change uriBuilder.build() generation of key with multiple values.

[robertobsc]

This issue relates with #200. As a workaround to call a function with multiple ids I call fetchConnections like this:

MultiValueMap<String, String> queryParams = new LinkedMultiValueMap<>();
usersIds.forEach(u->queryParams.add("ids", u));

List<JsonNode> posts = fetchConnections("", "posts", JsonNode.class, queryParams, IPost.ALL_FIELDS);

But the uriBuilder.build() transform the "ids" map differently from expected: instead of : ids=a,b,c it does: ids=a&ids=b&ids=c

Facebook API gets only the first one "ids" or "id" key it finds. The others are ignored.

I request chaning the generation for the uri to ids=a,b,c