Add features and tidy comments

-Add feature to check if the login was successful by parsing telnet
output for a valid privileged-exec prompt (Cisco)
-Add working hosts.csv file
-Add report at the end of the script so that the user can see hosts that
were not reachable and hosts that were reachable but had an invalid
login.
-Comment the entire script so that it can be easily understood.
-Add some TODOs in the comments that will need to be fixed and worked on
later.