shorten README file extension
Complete the slim-based dzslides backend
fix typo in footer, use loop for common meta
fix use of single quotes for attribute
cleanup templates

- remove unnecessary endlines
- don't quote interpolated strings
- use #{@property} syntax instead of #@property
- don't chomp
cleanup dzslides backend

- make class names consistent w/ html5 backend
- add speaker notes detection & output
- setup theme defaults in header
- remove unnecessary class names
- fix section title
- add helpers
- fix source blocks
- don't wrap openblock in content div