[X] Eps (unstructured doc) support
[X] Check input params in public methods
[/] API Documentation
[X] Printing API (Exporter)
[X] spectre_document_save if make sense
[X] Fill README file
[X] Makefile for ghostscript dir. It's not installale but it's distribuible
[ ] spectre_document_load_from_data
[ ] spectre_document_save_to_data
[X] A convenient function spectre_document_render for unstructured documents