Lexer testcases for symbol parsing.
Grammar rules for symbols.
Lexer states for symbol literals.
Right, the lexer tokens include " and #{.
AST tests for symbols.
AST node for symbol literals.
Parse symbols both literal and interpolated.

Refactor some common functionality into utility methods.
Visit symbol nodes as part of the AST.
Print symbols in the AST printer.
Whoops, wrong visitor method.
Distinguish between SYMBOLS and QUOTEDSYMBOLS.

Might as well do the lifting in the lexer, here.
Merge pull request #11 from smashwilson/symbols

Symbols.