Fix bug with lookahead
======================
The way that lookahead works right now is broken.
We don't take in count the following cases
of a group, or the remainig iterations of a loop.
Examples:
ab(c.*de)fg
will match "abcfg", cause when we reach the .*, we have
no way of knowing that we also have a de ahead, not only
the fg.
ab(c.*){2,3}
won't match abcc, cause in the first iteration of (c.*) the
wildcard will eat up all the characters, not knowing that
the (c.*) group will be matched again.
We need a more sophisticated way of storing lookahead cases
in the RegexCtx