Added GitHubApiUrl and GitHubDomain to settings and template
Put values from settings into handler/auth.go
Use custom github domain for webhook
Update all github clients in code
Added settings to github_add page (fix redirect)
Fixed identation
Make IsGit check less strict
Fixed another github client instance in code
Migration file based on #83

I choosed Rev3, because Rev2 will be about "open invitations" feature.
Merge pull request #75 from floatdrop/github-enterprise-support

GitHub Enterprise Support
removed unused migration sample file
Merge remote-tracking branch 'origin/master'
fixed compile error in migration script
altered migration to set default github domain and url
removed github domain and url from schema.go for unit tests
Keep indices when dropping/renaming columns.
Add func to fetch SQL definition for indices.

Also rearrange sql.Result and err declaration.
Fix index operations:

- Pass args as variadic params
- Tests for index operations
- Refactor fetchColumns
Refactor columns matching method
Add shell script to generate migration script.