Add support for print pdf from the command line

Yet another wrapper feature from reveal.js.
This leverages the reveal.js print-pdf plugin by passing the server
the `--print` (or `-r`) parameter.

It will try to build the pdf based on the initial file that the server
loads. So if no file is passed to the server the print-pdf will build
a pdf for the server listing, ie `reveal-md --print blah.pdf` will
produce a pdf of the whole server listing of markdown files.
Update print directions
Update path to branch (temporarily)
Better handle file name source and output

Fix a bug where printMode was not always accurate or when the print
parameter was given no input (which is fine), but didn't want the
filename for the PDF to be 'true.pdf'.
Revert package info back to origin
Add comments to filename regex for markdown files
Merge pull request #10 from samtsai/print_plugin_support

Print plugin support