minor fixes

Author: fernandezpablo85

src/main/java/org/scribe/extractors/HeaderExtractorImpl.java

@@ -16,6 +16,7 @@ public class HeaderExtractorImpl implements HeaderExtractor
 {
   private static final String PARAM_SEPARATOR = ", ";
   private static final String PREAMBLE = "OAuth ";
+  public static final int ESTIMATED_PARAM_LENGTH = 20;
 
   /**
    * {@inheritDoc}
@@ -24,7 +25,7 @@ public String extract(OAuthRequest request)
   {
     checkPreconditions(request);
     Map<String, String> parameters = request.getOauthParameters();
-    StringBuffer header = new StringBuffer(parameters.size() * 20);
+    StringBuilder header = new StringBuilder(parameters.size() * ESTIMATED_PARAM_LENGTH);
     header.append(PREAMBLE);
     for (Map.Entry<String, String> entry : parameters.entrySet())
     {

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

@@ -1,9 +1,6 @@
 package org.scribe.model;
 
-import java.io.UnsupportedEncodingException;
-import java.net.URLEncoder;
-import org.scribe.exceptions.OAuthException;
-import org.scribe.utils.OAuthEncoder;
+import org.scribe.utils.*;
 
 /**
  * @author: Pablo Fernandez