build cleanups

* update docs to simplify build steps
* Gemfile.lock seemed to have an older version specified
* do not check in the pkg dir

ruby/.gitignore

@@ -4,3 +4,4 @@ tags
 lib/google/protobuf_java.jar
 protobuf-jruby.iml
 target/
+pkg/

ruby/Gemfile.lock

 PATH
   remote: .
   specs:
-    google-protobuf (3.0.0.alpha.2)
+    google-protobuf (3.0.0.alpha.3.1.pre)
 
 GEM
   remote: https://rubygems.org/

ruby/README.md

@@ -76,7 +76,7 @@ Then install the required Ruby gems:
 Then build the Gem:
 
     $ rake gem
-    $ gem install pkg/protobuf-$VERSION.gem
+    $ gem install `ls pkg/google-protobuf-*.gem`
 
 To run the specs: