Updated install guide, not about index update

Author: alebedev

README.md

@@ -82,20 +82,23 @@ that is. If you want to upload & delete the local cache of media files, run:
 
 $ git media clear
 
+If you want to replace file in git-media with changed version (for example, video file has been edited),
+you need to explicitly tell git that some media files has changed:
+
+ $ git update-index --really-refresh
+
+
 ## Config Settings
 
 $ git config --global media.auto-download false
 
 
 ## Installing
 
- $ sudo gem install trollop
- $ sudo gem install s3
- $ sudo gem install ruby-atmos-pure
- $ sudo gem install right_aws
- $ sudo gem install net_dav
+ $ sudo gem install bundler
+ $ bundle install
  $ gem build git-media.gemspec
- $ sudo gem install git-media-0.1.3.gem
+ $ sudo gem install git-media-*.gem
 
 ## Notes for Windows