SignatureCalculator for ning client and new version

[vonagam]

As is seen here, ning removed url parameter from calculateAndAddSignature method in newer version of the library:

https://github.com/AsyncHttpClient/async-http-client/blob/1.9.x/src/main/java/com/ning/http/client/SignatureCalculator.java#L38

httpsig-java/http-helpers/src/main/java/net/adamcin/httpsig/http/ning/AsyncSignatureCalculator.java

Line 58 in 2b1fc56

public void calculateAndAddSignature(String url, Request request, RequestBuilderBase<?> requestBuilder) {

As this parameter is not used in any way by AsyncSignatureCalculator it can be simply removed to support new interface.

Can http-helpers be updated with support for newer ning client version?