Add HTML5 Boilerplate template

Given the need for something to build, I've decided this is the perfect
opportunity to give the HTML5 Boilerplate template a thorough test run
(v4.3.0).

Downloaded latest stable release from Github and included into the
project.

Note: Renamed original README.md to README-html5-boilerplate.md.
Add title to index.html

This app needs a title, so let's do something simple. Say, Heroku Test
01?
Convert index from HTML to PHP

Upon deployment of our HTML application, Heroku returns the following
message: "Push rejected, no Cedar-supported app detected".

> "Celadon Cedar is Heroku’s default runtime stack and is a flexible,
polyglot environment with robust introspection and erosion-resistance
capabilities."

Cedar supports frameworks such as Python, Django, Rails, etc. However,
a plain HTML application is not supported. Therefore, in order to
deploy our first application to Heroku a Cedar-supported language or
framework must be implemented.

PHP is a Cedar-supported language. As such, simply converting the index
file from HTML to PHP resolves the issue.