added convenience methods for the builder api

src/main/java/org/scribe/builder/ServiceBuilder.java

@@ -20,6 +20,7 @@ public class ServiceBuilder
   private String callback;
   private Api api;
   private String scope;
+  private SignatureType signatureType;
   
   /**
    * Default constructor
@@ -122,6 +123,19 @@ public class ServiceBuilder
     this.scope = scope;
     return this;
   }
+
+  /**
+   * Configures the signature type, choose between header, querystring, etc. Defaults to Header
+   *
+   * @param scope The OAuth scope
+   * @return the {@link ServiceBuilder} instance for method chaining
+   */
+  public ServiceBuilder signatureType(SignatureType type)
+  {
+    Preconditions.checkNotNull(type, "Signature type can't be null");
+    this.signatureType = type;
+    return this;
+  }
   
   /**
    * Returns the fully configured {@link OAuthService}
@@ -133,6 +147,6 @@ public class ServiceBuilder
     Preconditions.checkNotNull(api, "You must specify a valid api through the provider() method");
     Preconditions.checkEmptyString(apiKey, "You must provide an api key");
     Preconditions.checkEmptyString(apiSecret, "You must provide an api secret");
-    return api.createService(new OAuthConfig(apiKey, apiSecret, callback), scope);
+    return api.createService(new OAuthConfig(apiKey, apiSecret, callback, signatureType), scope);
   }
 }

src/main/java/org/scribe/model/OAuthConfig.java

@@ -16,12 +16,19 @@ public class OAuthConfig
   {
     this(key,secret,null);
   }
-  
+
+  //Kept for backwards compatibility
   public OAuthConfig(String key, String secret, String callback)
+  {
+    this(key,secret,callback,null);
+  }
+
+  public OAuthConfig(String key, String secret, String callback, SignatureType type)
   {
     this.apiKey = key;
     this.apiSecret = secret;
     this.callback = callback;
+    this.signatureType = type;
   }
 
   public String getApiKey()