v3.3

Changes to Language Definition

• Defined Minimal NestedText, a subset of NestedText.
• NestedText document files should end with a newline.

Changes to Python Implementation

• add normalize_key argument to load and loads.
• added utility functions for operating on keys and keymaps:
  • get_value_from_keys
  • get_lines_from_keys
  • get_original_keys
  • join_keys
• None passed as key is now converted to an empty string rather than "None".