Added bunch of javadocs and restricted some visibility.

No functional changes

src/main/java/org/scribe/builder/api/TwitterApi.java

@@ -3,13 +3,13 @@ package org.scribe.builder.api;
 public class TwitterApi extends DefaultApi10a
 {
   @Override
-  public String getAccessTokenEndpoint()
+  protected String getAccessTokenEndpoint()
   {
     return "http://twitter.com/oauth/access_token";
   }
 
   @Override
-  public String getRequestTokenEndpoint()
+  protected String getRequestTokenEndpoint()
   {
     return "http://twitter.com/oauth/request_token";
   }