Update .gitignore for YARD-generated files.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Document Extruder::Config#initialize options.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Remove documentation for removed parameter.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>