Add jruby docs

jruby/README-short.txt

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+JRuby (http://www.jruby.org) is an implementation of Ruby (http://www.ruby-lang.org) on the JVM.

jruby/content.md

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+# What is JRuby?
+
+JRuby (http://www.jruby.org) is an implementation of Ruby (http://www.ruby-lang.org) on the JVM.
+
+Ruby is a dynamic, reflective, object-oriented, general-purpose, open-source
+programming language. According to its authors, Ruby was influenced by Perl,
+Smalltalk, Eiffel, Ada, and Lisp. It supports multiple programming paradigms,
+including functional, object-oriented, and imperative. It also has a dynamic
+type system and automatic memory management.
+
+> [wikipedia.org/wiki/Ruby_(programming_language)](https://en.wikipedia.org/wiki/Ruby_(programming_language))
+
+JRuby leverages the robustness and speed of the JVM while providing the same
+Ruby that you already know and love.
+With JRuby you are able to take advantage of real native threads, enhanced
+garbage collection, and even import and use java libraries.
+
+# How to use this image
+
+## Create a `Dockerfile` in your Ruby app project
+
+    FROM jruby:.1.7.15-onbuild
+    CMD ["./your-daemon-or-script.rb"]
+
+Put this file in the root of your app, next to the `Gemfile`.
+
+This image includes multiple `ONBUILD` triggers which should be all you need to
+bootstrap most applications.  The build will `COPY . /usr/src/app` and `RUN
+bundle install`.
+
+You can then build and run the Ruby image:
+
+    docker build -t my-ruby-app .
+    docker run -it --name my-running-script my-ruby-app
+
+## Run a single Ruby script
+
+For many simple, single file projects, you may find it inconvenient to write a
+complete `Dockerfile`. In such cases, you can run a Ruby script by using the
+Ruby Docker image directly:
+
+    docker run -it --rm --name my-running-script -v "$(pwd)":/usr/src/myapp -w /usr/src/myapp jruby:1.7.15 jruby your-daemon-or-script.rb

jruby/license.md

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+View [license information](https://github.com/jruby/jruby/blob/master/COPYING)
+for the software contained in this image.