code: public String computeSignature(String requestMethod, String targetUrl, Map<String, String> params) {
          return computeSignature(requestMethod, targetUrl, params, consumerSecret, tokenSecret);
      }
docs: Computes the signature for an oauth/request_token request per
  {@link https://dev.twitter.com/oauth/overview/creating-signatures}.
  Expects consumerSecret and tokenSecret to already be set to the desired values.
  
  @param requestMethod
  @param targetUrl
  @param params
  @return