Increase deck2pdf delay to allow manual load

[Issue #4]

For some reason, the title page cannot be loaded in deck2pdf preview. By
increasing delay before generating PDF pages, I can manually scroll to
the next slide and back, allowing the title page to load.
Use Rakefile in place of Makefile

Rakefile is sufficient and easier to understand.
Add script to generate FontForge script

[Issue #4]

This Ruby script extracts all non-ASCII characters from main.md, keep
only one instance for each distinct character, and generate a file
containing these chars, and a FontForge script that can subset a font
file so we have a minimum font that can be used to display these
characters.
Add tasks for rakefile

[Issue #4]

The file now support pdf and clean tasks.
Simulate larger viewport when exporting PDF

[Issue #4]

Use 1024x768 to avoid aliases when projecting.