[ADD] $?

dev/TODO

@@ -1,9 +1,6 @@
 - finding commands
 	- built-in commands
-- signals
-	- ^C, ^D, ^\
 - variables
-	- $?
 	- uses $PATH in env.variables instead of envp
 - builtins:
 	- echo		(with option -n)
@@ -17,6 +14,7 @@
 	- empty variables aren't freed
 	- need to free value returned by readline
 	- the builtins should get all arguments and check if they're good
+	- command `echo "hello` with unclosed quotes
 
 (unnecessary part)
 - working history (rl_* functions?)