Fix sudo false positive

[reverbc]

Issue details

This PR is intended to fix #23 False positive on the use of SUDO

Steps to reproduce/test case

The test cases have been included in this PR, contains the following scenario in test case:

/usr/bin/sudo rm -rf /  # absolute path to sudo binary
 	  sudo rm -rf /  # spaces and tabs before sudo
date; sudo rm -rf /  # semicolon before sudo
date; sudo  # sudo in end of sentence
echo "jenkins ALL=(ALL) ALL" >> etc/sudoers  # false alarm for sudoers file
yum list installed | grep sudo  # false alarm for not using sudo