Remove TransformPipeline from our public API

DocumentTransform remains visible to allow others to implement
transforms, but the pipeline itself doesn't need to be available for
others.

src/com/google/enterprise/adaptor/TransformPipeline.java

diff --git a/src/com/google/enterprise/adaptor/TransformPipeline.java b/src/com/google/enterprise/adaptor/TransformPipeline.java
index b411d15..f9f6ecb 100644
--- a/src/com/google/enterprise/adaptor/TransformPipeline.java
+++ b/src/com/google/enterprise/adaptor/TransformPipeline.java
@@ -27,7 +27,7 @@
  *
  * <p>This class is thread-safe.
  */
-public class TransformPipeline {
+class TransformPipeline {
   private final List<DocumentTransform> transformList;
   private final List<String> names;