Fix a minor bug in the lexer (it would not match the last character of the input) and add Lexer tests.

main.cpp

@@ -19,6 +19,7 @@
 int main(int argc, char* argv[]) {
 	if (argc == 2 && std::string(argv[1]) == "--test") {
 		StringReader::test();
+		Lexer::test();
 		return 0;
 	}