Rename repo from vulcan to vulcan-sql

## **What’s the problem you're trying to solve**
Our project name is confused with other projects.

## **Describe the solution you’d like**
Rename the repository from `vulcan` to `vulcan-sql`. Github will automatically redirect the URLs to the new one. Following services might be impacted:

- Circle CI
- Codecov
- Badges (readme)

## **Additional context**