Add a https clone button for repositories

This button will be responsive so that it's still usable on mobile. The clone button triggers a popover that contains the `hg clone` command for the current repository and a quick copy to clipboard button.

Testing Done:
1. Setup `.hg/hgrc` file on the repo i'll test on and add a value for `http_clone_url` under the `web` section.
2. Run `hg serve`
3. Verified the clone button appears.
4. Verified the copy button copies the entire `hg clone ` to the clipboard
5. Verified the repository title and the clone button behaves in a responsive manner (ie on mobile they are split into two lines)

Bugs closed: HGKEEPERTHEME-11

Reviewed at https://reviews.imfreedom.org/r/194/