Visualize NFA with DOT language

[Lai-YT]

Motivation

regexp converts the regular expression into an NFA before simulating.
We would like to see what such NFA looks like, which is valuable in learning how Thompson's algorithm works.

This feature bumps the version to 0.1.0.

What's new?

• A nfa2dot function that traverses the NFA and does the conversion
• Command line options --graph (-g) and --output (-o) on using the graph mode and specifying the output dot file

Breaking change

• The short option for getting the version number is now -V instead of -v. -v is preserved for the possible use of verbose.

How has this been tested?

A test script cli_test.sh feeds arguments the regexp and checks the exit code.

# Give permission on execution
$ chmod +x cli_test.sh

# Run CLI tests
$ ./cli_test.sh

Checklist

I have completed the following:

• Added appropriate comments to my code where the code is not easily understood.
• Updated the relevant documentation.
• Added tests to cover the proposed changes (and if not, explain why).

Resolves: #1