Variables and templates support

This release offers a new variable and template system that uses variables (prefixed by $)

$name: JD Lien
$title: Senior Full-Stack Software Engineer
$location: Edmonton, Alberta, Canada

These variables can then be used within templates, denoted by cury braces like

{{HEADING}}
{{CONTACT}}

This allows for a markdown file that is easier to edit and read while offloading the more complex HTML markup to the resume.py code.