Fix rubies 2.1.X and Add jruby

- Compile fix
- Pull rbenv ruby list ( If the image has not been builded recently that there are no new ruby versions  like 2.1.X )
- Add jruby 1.7.11 with openjdk6 and openjdk7 ( need test )
- Update readme

Also im try to add rbx, but got configure error, looks like some dependency not installed
```
Downloading yaml-0.1.6.tar.gz...
-> http://dqw8nmjcqpjn7.cloudfront.net/5fe00cda18ca5daeb43762b80c38e06e
Installing yaml-0.1.6...
Installed yaml-0.1.6 to /home/ubuntu/.rbenv/versions/rbx-2.2.6

Downloading rubinius-2.2.6.tar.bz2...
-> http://releases.rubini.us/rubinius-2.2.6.tar.bz2
Installing rubinius-2.2.6...

BUILD FAILED

Inspect or clean up the working tree at /tmp/ruby-build.20140404172047.110
Results logged to /tmp/ruby-build.20140404172047.110.log

Last 10 log lines:
Checking sizeof(long long): 8 bytes
Checking sizeof(float): 4 bytes
Checking sizeof(double): 8 bytes
Checking sizeof(off_t): 8 bytes
Checking sizeof(time_t): 8 bytes
Checking for libc version: ldd: missing file arguments
Try `ldd --help' for more information.
libc not found. Use the --libc configure option.

Running 'configure' failed. Please check configure.log for more details.
2014/04/04 21:21:51 build: The command [/bin/sh -c export PATH=$PATH:/home/ubuntu/.rbenv/bin                                         &&    cd ~/.rbenv/plugins/ruby-build                                                    &&    git pull                                                                          &&    export RBENV_VERSION=rbx-2.2.6                                                    &&    eval "$(rbenv init -)"                                                            &&    CC=gcc rbenv install rbx-2.2.6                                                    &&    rbenv rehash                                                                      &&    rbenv global rbx-2.2.6                                                            &&    rbenv rehash                                                                      &&    gem install bundler                                                               &&    rbenv rehash] returned a non-zero code: 1
```