Added version command for the cli using ldflags

[anveshthakur]

Hi @osteensco,
I've added the -version, -v command to show the version
It takes the release version from Github and then puts it into the program at the time of building the project

This PR is for the issue #15

[osteensco]

Thanks for the PR, can you add a couple of things:

• macOS support
• fastTravelCLI ASCII logo above the version output
• at least one unit test
• ensure your branch is caught up with master as I fixed some broken tests

I was reviewing this on my phone so apologies if your PR already addresses some of these and I just missed it.

[anveshthakur]

Hi @osteensco,

I've added all the changes you've listed down.
LMK if there is anything else you want me to change or add.

Thanks!

[osteensco]

Fixed a test that wasn't passing, thanks for the PR!