migrate project to Spoofax 1.3
migrate syntax to sdf3: remove template keyword, fix star-separator notation
migrate syntax to sdf3: lexical syntax to productive form
migrate pretty printer use to src-gen
up version number to 0.2.3
update readme to reflect Spoofax 1.3 dependency
Merge pull request #7 from metaborg/migrate-to-spoofax1.3-stable

Migrate to spoofax1.3 stable