cdnjs is a free distributed JS library delivery service.
Heroku is a cloud platform as a service (PaaS) supporting several programming languages.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
MathJax is a cross-browser JavaScript library that displays mathematical notation in web browsers, using MathML, LaTeX and ASCIIMathML markup.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Ruby on Rails is a server-side web application framework written in Ruby under the MIT License.
Ruby is an open-source object-oriented programming language.
WEBrick is a lightweight HTTP server library in Ruby, included in the standard library, primarily used for local development and testing of Ruby web applications.