Lexer Updates and Testing

[martin-bucinskas]

Description

The lexer class tests and improvements.

Issue 1

Inside the tests, the Lexer.lex method is called in a non static way despite lex being static.
There is no need to create an instance if lex is static.

Issue 2

Consider to use StringBuilder instead of StringBuffer as this will have performance has better performance.

Issue 3

There is an indentation error that you can spot in between lines 46 and 48 of Lexer.class.

Issue 4

Redundant private declaration for TokenType enum.