add ruby/ngx_mruby framework

Hello,

I was able to get this installed and running in a vagrant dev env.
It does exit after running the test, so there may be a bug in my code or the current suite.

Any pointers would be appreciated.

thanks
@matsumoto-r about this: 

> hardware thread means CPU core, right? 

it means parallel threads of execution. Normally, on AMD hardware, this means CPU cores. On Intel without hyper threading (e.g. older intel) it means CPU cores. On Intel with hyper threading, it means number of hardware threads, where each core has two. From [Wikipedia](https://en.wikipedia.org/wiki/Multithreading_%28computer_architecture%29): 

> [Hardware Threads] are distinguished from multiprocessing systems (such as multi-core systems) in that the threads have to share the resources of a single core: the computing units, the CPU caches and the translation lookaside buffer (TLB).

@methane - about this: 

> Can you use placement group on EC2 for low and stable network latency? 

I don't run the tests, so let's alert @msmith-techempower that this needs to be done. I'm not sure how TechEmpower configures the EC2 environment currently, perhaps they would be kind enough to use the scripts I wrote [here](https://github.com/TechEmpower/FrameworkBenchmarks/tree/master/deployment/vagrant-aws) and [here](https://github.com/TechEmpower/FrameworkBenchmarks/tree/master/deployment/vagrant-production) so the scripts define exactly the provisioning and deployment process and can be upgraded to include items such as choosing a placement group