0.4.18-remastered.4

• Fixed Lexer#showPosition() input slicing
• Added Lexer#eof() method
• Added parameter position for Lexer#showPosition()
• Changed Lexer#_input to contain entire input instead of unmatched input
• Removed Lexer#matched
• Removed Lexer#pastInput()
• Removed Lexer#upcomingInput()
• Restricted Lexer#unput() to allow unput only a part of match substring