Write test code

[cosmo0920]

• [x] Create unit test mechanism
  • [x] At least, Config type unit test
  • [ ] multi-line/singile-line format specification test
  • [x] Split to modules from single file
• [x] Decide how to test about command line
  • Command Line arguments are passed as string [] into main. So, this test target is CommandLineParser module
• [x] Use Paket to manage dependent packages
• [x] Build and test with mono platform (done https://github.com/cosmo0920/grnline.fs/commit/8d5867191eb5e296441f5590eb095003da53d77c and https://github.com/cosmo0920/grnline.fs/commit/f2506e0f778319099e4e1aea3a6a70c21d2821e2)
• [ ] integration tests? (optional)