Release v1.6.2

Added

• screenplay <file>.play compiles a single file. Pointing the tool at a file previously failed with Directory '<path>' does not exist, so verifying one generated document meant copying it into a scratch directory first. (#31)
• --warnaserror makes warnings fail the run with exit code 1, so a pipeline that generates documents can require them to be clean. (#31)
• IPlayFileCompiler.CompileFile(path) compiles one known .play file without going through directory discovery. (#31)