Added support for GitHub API Endpoint

Added ability to specify the GitHub API Endpoint to support
Enterprise accounts
remove trailing / from api endpoint
Merge branch 'github_enterprise'

Merge support for GitHub Enterprise API endpoints
Merge branch 'JHaals-ghe'

Merge pull request #201 from JHaals-ghe
Updated for v1.2.0

Updated version and Gemfile.lock for v1.2.0 gem release