`airship publish` add version verification

[BSteffaniak]

Verify that:

• new version is greater than the current version
  • if it is, then warn and prompt to exit
• new version does not skip any intermediate version values (e.g. jump from 1.0.0 to 1.3.5)
  • if it does, then warn and prompt to exit
• new version does not already exist as a remote tag
  • if it does, then warn and prompt to exit, otherwise overwrite the tag