README.md in ezid-client-1.9.3 vs README.md in ezid-client-1.9.4

@@ -126,24 +126,24 @@
 *Added in v1.3.0:* `Ezid::BatchDownload` class.
 
 ```
 >> batch_download = Ezid::BatchDownload.new(:csv)
  => #<Ezid::BatchDownload format=:csv>
- 
+
 >> batch_download.column = ["_id", "_target"]
  => ["_id", "_target"]
- 
+
 >> batch_download.createdAfter = Date.today.to_time
  => 2016-02-24 00:00:00 -0500
- 
+
 >> batch_download
  => #<Ezid::BatchDownload column=["_id", "_target"] createdAfter=1456290000 format=:csv>
- 
+
 >> batch_download.url
 I, [2016-02-24T18:03:40.828005 #1084]  INFO -- : EZID BatchDownload -- success: http://ezid.cdlib.org/download/4a63401e17.csv.gz
  => "http://ezid.cdlib.org/download/4a63401e17.csv.gz"
- 
+
 >> batch_download.file
  => /current/working/directory/4a63401e17.csv.gz
  ```
 
 ## Batch
@@ -153,17 +153,17 @@
 **Version 1.7.0 upgrade note:** This class was originally named `Ezid::BatchEnumerator`, but it is not a Ruby enumerator. `Ezid::Batch` is the new name with the same API.
 
 ```
 >> require 'ezid/batch'
  => true
- 
+
 >> batch = Ezid::Batch.new(:anvl, "spec/fixtures/anvl_batch.txt")
  => #<Ezid::Batch:0x007f87a8900308 @format=:anvl, @batch_file="spec/fixtures/anvl_batch.txt">
- 
+
 >> id = batch.first
  => #<Ezid::Identifier id=ark:/99999/fk4086hs23>
- 
+
 >> id.target
  => "http://example.com"
 
 >> puts id.metadata
 _updated: 1488227717
@@ -315,9 +315,18 @@
 ## Running the ezid-client tests
 
 See http://ezid.cdlib.org/doc/apidoc.html#testing-the-api.
 
 In order to run the integration tests successfully, you must supply the password for the test account "apitest" (contact EZID).  To run the test suite without the integration tests, use the `rake ci` task.
+
+## Dockerfile
+
+A basic Dockerfile is provided based on Docker official Ruby image tags.
+
+An example building an image with the latest Ruby and running the unit tests:
+
+    $ docker build -t ezid-client .
+    $ docker run --rm -it ezid-client bundle exec rspec ./spec/unit/
 
 ## Contributing
 
 1. Fork it ( https://github.com/[my-github-username]/ezid-client/fork )
 2. Create your feature branch (`git checkout -b my-new-feature`)