v0.5.1

• Created abstract resolve_reference function in codegen
  This function will resolve entity references (whether object
  references or self references, rvalues or lvalues) and return a
  pointer to the referenced entity, as well as compiled code necessary
  to access it, debug information about that compiled code (whether
  temporary variables were necessary in the compiled code), and
  optional error information if the reference could not be resolved
  This removes a lot of code duplication in handling references
• Fixed example code display on spec page for 'super'
• Error reporting:
  Cast tokens to CommonToken before throwing an error or warning
  This should at least mostly eliminate 'Position Unknown' errors
  in our error reporting.
  Manually override ANTLR4's broken token position tracking
  ANTLR4's system routinely returns incorrect values for
  token->getLine() and token->getCharPositionInLine(). This is
  screwing with our error reporting. So we'll just track it ourselves
  in our emit() override.
• Store an intermediary code buffer between the compiler and the
  output stream
  Do not immediately write code to the output stream.
  In the case of '-o -', this clutters the output when errors are
  present.