Create tech stack docs (techstack.yml and techstack.md)

[stack-file]

Adding tech stack documentation to allow anyone to easily see what is being used in this repo without digging through config files. Two files are being added: techstack.yml and techstack.md. techstack.yml contains data on all the technologies being used in this repo. techstack.md is a visualization of the YML file and displays the tech stack data in a pretty Markdown file.

💡 Protip: techstack.md contains a comment at the top of the file that the following README snippet (with and without the logos) at the top of the file as a comment:

<--- Readme.md Snippet without images Start --->

Tech Stack

stackshareio/omniauth is built on the following main stack:

• Ruby – Languages
• RSpec – Testing Frameworks
• Bundler – Front End Package Manager
• Travis CI – Continuous Integration

Full tech stack here

<--- Readme.md Snippet without images End --->

Get the code:

## Tech Stack
stackshareio/omniauth is built on the following main stack:

- [Ruby](https://www.ruby-lang.org) – Languages
- [RSpec](https://rspec.info/) – Testing Frameworks
- [Bundler](http://bundler.io) – Front End Package Manager
- [Travis CI](http://travis-ci.com/) – Continuous Integration

Full tech stack [here](/techstack.md)

---

<--- Readme.md Snippet with images Start --->

Tech Stack

stackshareio/omniauth is built on the following main stack:

• Ruby – Languages
• RSpec – Testing Frameworks
• Bundler – Front End Package Manager
• Travis CI – Continuous Integration

Full tech stack here

<--- Readme.md Snippet with images End --->

Get the code:

## Tech Stack
stackshareio/omniauth is built on the following main stack:

- <img width='25' height='25' src='https://img.stackshare.io/service/989/ruby.png' alt='Ruby'/> [Ruby](https://www.ruby-lang.org) – Languages
- <img width='25' height='25' src='https://img.stackshare.io/service/2539/logo.png' alt='RSpec'/> [RSpec](https://rspec.info/) – Testing Frameworks
- <img width='25' height='25' src='https://img.stackshare.io/service/2988/4e77LXIo_400x400.png' alt='Bundler'/> [Bundler](http://bundler.io) – Front End Package Manager
- <img width='25' height='25' src='https://img.stackshare.io/service/460/Lu6cGu0z_400x400.png' alt='Travis CI'/> [Travis CI](http://travis-ci.com/) – Continuous Integration

Full tech stack [here](/techstack.md)