Add RegularExpression.cpp.

1. Use node graph to express pattern.
2. do match by graph search.(DFS??)

Signed-off-by: Wayne Wang <wythern@gmail.com>
Update RegularExpression.cpp

1. Use more flags to record status.
2. Deconstructor has double free issue.
need debugging.

Signed-off-by: Wayne Wang <wythern@gmail.com>