[Fix] Return valid line locations for code with no ast or nil nodes
Clean up line numbers code
Make AST Node wraper for line number s-expression nodes
Separate out sexp node dresser
Simplify line/method checking
LineNumbers parsing should rescue StandardError, not Exception
Update history
Merge pull request #137 from bf4/cleanup_line_number_processing

Ensure valid line number locations. Cleanup line number processing, introduce SexpNode