sourceror

1. Enhancements

• [Sourceror] - Add Sourceror.get_meta/1, Sourceror.get_args/1,
  Sourceror.get_line/2, Sourceror.get_column/2 and
  Sourceror.get_end_line/2.
• [Sourceror] - Add Sourceror.update_args/2.
• [Sourceror] - Add Sourceror.get_start_position/2,
  Sourceror.get_end_position/2, Sourceror.get_range/1 and
  Sourceror.get_line_span.
• [Sourceror] - Add Sourceror.compare_positions/2.
• [Sourceror] - Sourceror.correct_lines/3 now corrects comments line
  numbers, preserving the relative numbers from the associated node.
• [Sourceror.Comments] - Sourceror.Comments.extract_comments/1 now preserves
  the comments line numbers.

2. Bug Fixes

• [Sourceror] - Now Sourceror.postwalk/3 correctly propagates line
  corrections to parent nodes.
• [Sourceror] - Now Sourceror.postwalk/3 corrects end line numbers(end,
  closing, end_of_expression) appropiately.