Sslstrip proper error handling

- Fixes #214
- fixed two probable memory leaks. New regexes were being compiled, but never freed.  
 - The fix should make sslstrip faster since it only has to compile the regexes once. 
- fixed broken redir_command_* exit status checking. Now also logging the command that failed to execute. 


Thanks to @AntonioCollarino, even though I didn't end up using his patch (#220)!