better error messages when scribe can't establish a network connection

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

@@ -59,9 +59,14 @@ class Request
     {
       createConnection();
       return doSend();
-    } catch (IOException ioe)
+    }
+    catch (UnknownHostException uhe)
     {
-      throw new OAuthException("Problems while creating connection", ioe);
+      throw new OAuthException("Could not reach the desired host. Check your network connection.", uhe);
+    }
+    catch (IOException ioe)
+    {
+      throw new OAuthException("Problems while creating connection.", ioe);
     }
   }
 

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

@@ -28,10 +28,11 @@ public class Response
       code = connection.getResponseCode();
       headers = parseHeaders(connection);
       stream = wasSuccessful() ? connection.getInputStream() : connection.getErrorStream();
-    } catch (UnknownHostException e)
+    }
+    catch (UnknownHostException e)
     {
       code = 404;
-      body = EMPTY;
+      body = Response.EMPTY;
     }
   }