Generalized a Lexeme to maintain the position of anything. Added Lexeme as a monoid around several datas of the AST and it's parameters
Opens the state before printing
Position now defined in Language.
Lexer now return a (Lexeme Token) to the Parser. Lexeme now hold a Position, not a AlexPosn
Changed te rules to maintain the Lexeme in the AST, according to the Language module. Changed functions to work with (Lexeme Token) instead of Token
Changed functions to work with (Lexeme a). Now reporting line and column number accordingly. Consider remove 'currPosn' of CheckState
merged master with this, still need to merge the Printer part.
merged the Printer.
Merge branch 'master' into prueba

* master:
  Arreglado el warning del pattern matching en el Printer
  Algunos cambios al printer
  Agregado un pretty printer para expresiones y para algunas instrucciones
  Agregadas algunas verificaciones sencillas sobre otros statements. Pasando a hacer un pretty printer para los statements
  Agregado analisis parcial de condicionales, agregadas las reglas para manejar condicionales en la gramatica
  Cambiadas mas listas por sequences
  Cambiados los list por sequence en donde se manejaban listas de statements y en donde se manejaban listas de variables