Added -s/-f flags to skip/force token validation

[shreyb]

As discussed in issue #130, if stdout is a TTY, we will keep the current default behavior of verifying the token. If stdout is not a TTY, we will skip verification of the token by default. The default behavior can be overridden using the -s/-f flags.

Closes #130

[shreyb]

These are the tests I ran:

Interactive (TTY): PASS

• -s --> skip verification
• default --> don't skip verification
• -f --> force verification
• -f and -s: error

Non-interactive (from a script) (NOT a TTY): PASS

• -s ---> skip verification
• default ---> skip verification
• -f --> force verification
• -f and -s: error

Script to check non-interactive case:

/path/to/copy/of/htdecodetoken "$@" > /tmp/htdecodetoken.log 2>&1
echo "Is TTY?" >> /tmp/htdecodetoken.log
echo "  $(test -t 1 && echo "yes" || echo "no")" >> /tmp/htdecodetoken.log
echo "Args: $@" >>  /tmp/htdecodetoken.log
cat /tmp/htdecodetoken.log
exit