How to build jar file.

```
> rvm -v
rvm 1.29.2 (latest) by Michal Papis, Piotr Kuczynski, Wayne E. Seguin [https://rvm.io/]
```

```
> rvm list

rvm rubies

=* ruby-2.2.6 [ x86_64 ]

# => - current
# =* - current && default
# * - default
```
```
> warble jar & java -jar redis-stat.jar
[1] 25834
rm -f redis-stat.jar
Creating redis-stat.jar
Ignoring eventmachine-1.2.3 because its extensions are not built. Try: gem pristine eventmachine --version 1.2.3
Ignoring json-1.8.6 because its extensions are not built. Try: gem pristine json --version 1.8.6
Ignoring thin-1.5.1 because its extensions are not built. Try: gem pristine thin --version 1.5.1
LoadError: no such file to load -- puma
require at org/jruby/RubyKernel.java:961
require at uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:54
block in Server at uri:classloader:/redis-stat/lib/redis-stat/server.rb:13
configure at uri:classloader:/gems/sinatra-1.3.6/lib/sinatra/base.rb:1356
at uri:classloader:/redis-stat/lib/redis-stat/server.rb:11
at uri:classloader:/redis-stat/lib/redis-stat/server.rb:7
at uri:classloader:/redis-stat/lib/redis-stat/server.rb:6
require at org/jruby/RubyKernel.java:961
(root) at uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:1
at uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:54
require at org/jruby/RubyKernel.java:961
(root) at uri:classloader:/redis-stat/lib/redis-stat.rb:6
at uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:1
load at org/jruby/RubyKernel.java:979
at uri:classloader:/META-INF/jruby.home/lib/ruby/stdlib/rubygems/core_ext/kernel_require.rb:54
require at org/jruby/RubyKernel.java:961
(root) at uri:classloader:/redis-stat/bin/redis-stat:4
at uri:classloader:/META-INF/main.rb:1
ERROR: org.jruby.embed.EvalFailedException: (LoadError) no such file to load -- puma
```