Display URL of git remote

[raghubetina]

We should make it clear in the UI what the URL of the current git remote is, to give confidence whether students created their workspace based on a fork or parent or (eventually) whether it's pointing to a Heroku remote, etc.

https://piazza.com/class/kmw9g9ibzrr7w?cid=19

[jelaniwoods]

Closed in #99