Update Simple.flex

Changed the fallback character from . to [^] since this serves as a basis of other lexers.

simple_language_plugin/src/com/simpleplugin/Simple.flex

@@ -41,4 +41,4 @@ KEY_CHARACTER=[^:=\ \n\t\f\\] | "\\ "
 
 ({CRLF}|{WHITE_SPACE})+                                     { yybegin(YYINITIAL); return TokenType.WHITE_SPACE; }
 
-.                                                           { return TokenType.BAD_CHARACTER; }
+[^]                                                         { return TokenType.BAD_CHARACTER; }