Almost complete rewrite:
* Slides are now parsed as HTML using handlebars-layouts (to allow for slide templates)
* Slides are stored in slides/*.htm and read in alphabetical order of filename (Directory can be changed in config)
* Slide templates are stored in slide-templates/*.htm and their filename is used in the slide HTML in a handlebars #extend block (Directory can be changed in config)
* Code has been split up into multiple files, stored in lib folder