Removed PDF conversion and all file input/output

All of textplay's previously built-in file input and output
functionality, and conversion (via 3rd party) to PDF, can be
accomplished using standard Unix redirects on the command-line.
Reproducing this inside textplay itself was cumbersome and unnecessary.
Textplay will remain a more Unix-like tool.
Bugfixes for empty line requirements after sluglines and dialogue
Notes are ignored when looking for empty lines around dialogue, scene
headings
Added makefile, updated documentation
Merge branch 'master' of https://github.com/olivertaylor/Textplay

# By Oliver Taylor
# Via Oliver Taylor
* 'master' of https://github.com/olivertaylor/Textplay:
  Added makefile, updated documentation
  Notes are ignored when looking for empty lines around dialogue, scene headings
  Bugfixes for empty line requirements after sluglines and dialogue
  Removed PDF conversion and all file input/output