refactor: rename module -> block within xmodule

xmodule/seq_block.py

@@ -1,5 +1,5 @@
 """
-xModule implementation of a learning sequence
+XBlock implementation of a learning sequence
 """
 
 # pylint: disable=abstract-method
@@ -39,7 +39,7 @@ from .exceptions import NotFoundError
 from .fields import Date
 from .mako_block import MakoTemplateBlockBase
 from .progress import Progress
-from .x_module import AUTHOR_VIEW, PUBLIC_VIEW, STUDENT_VIEW
+from .x_module import AUTHOR_VIEW, PUBLIC_VIEW
 from .xml_block import XmlMixin