✨ Add -v to show current moban version

[CLiu13]

Closes #107

Before raising the PR, here is a check list:

1. have you written unit tests for your code changes?
2. have you run "make format"?
3. are you requesting to "dev"?
4. have you updated the change log?
5. do you think that you can understand your changes after 6 month?
   5.1) can someone else understand your changes without your explanation?
6. are you pround of your code changes?
   6.1) do you have the feeling of achievement?
7. please add your name and github link to contributors.rst in alphabetical order.

[chfw]

A unit test case please！

[chfw]

I will look at the unit test failure.

[CLiu13]

I will look at the unit test failure.

Thanks. Not sure why it is occurring. New unit test case added for this change.

[codecov-io]

Codecov Report

Merging #179 into dev will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              dev     #179      +/-   ##
==========================================
+ Coverage   97.82%   97.83%   +<.01%     
==========================================
  Files          40       40              
  Lines        2071     2079       +8     
==========================================
+ Hits         2026     2034       +8     
  Misses         45       45

Impacted Files	Coverage Δ
moban/main.py	100% <100%> (ø)	⬆️
...sts/integration_tests/test_command_line_options.py	98.34% <100%> (+0.03%)	⬆️
moban/constants.py	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 986d545...a309bf7. Read the comment docs.

[chfw]

One more thing: update change log :)

Changes have addressed this review

[CLiu13]

One more thing: update change log :)

Done!

[chfw]

GTG