Lexer done

A simple lexer.
EOF, REAL_LITERAL, INTEGER_LITERAL, PLUS, MINUS, STAR, SLASH, PERCENT,
LEFT_PAR, RIGHT_PAR, ASSIGN, EQUALS, NOT_EQUALS, GREATER_THAN,
LESS_THAN, GOE_THAN, LOE_THAN, NOT, AND, OR, TRUE, FALSE, IDENTIFIER,
IF, ELSE, END, PRINT, COMA, STRING, TO, METHOD, VAR, WHILE, FOR, STEP,
NEED, RETURN