[semver:minor] Fix for GitHub Enterprise support

[motionsuggests]

Fixes https://github.com/CircleCI-Public/github-cli-orb/issues/21

Changes:

• GITHUB_TOKEN and GITHUB_HOSTNAME are exported in the release script because they are needed to make GitHub Enterprise work.
• In the steps for release I replaced setup with install because setup is causing the error in #21.
• token and hostname params are moved to the run step for release because they will be needed.
• Updated descriptions to mentionGITHUB_HOSTNAME and it's use.
• Updated the orb version numbers in examples.

I'm not 100% sure this is the correct approach. If user were relying on release to call setup this would break for them. I suppose an alternative would be to make an enterprise_release job and make it work only for enterprise.

Related Issue https://github.com/CircleCI-Public/github-cli-orb/issues/9

[KyleTryon]

Sorry this slipped through @motionsuggests, the addition looks great. Pushing through the tests now and merging as a patch after.

[motionsuggests]

Thanks @KyleTryon !