Fix CircleCI token example

[haythem]

The CircleCI token example contains a redundant fragment /circleci/circleci/:token.

In addition, I think that you should allow a comment or a hint to be associated with the example or the provider at least to guide the user especially with private repositories.

For instance, in CircleCI, there are 3 token scopes :

1. status used for build status
2. view-builds for downloading artifacts
3. all to grant full read access to the project

Although it might seem that the first type is the one that should be used with the badge, the badge will not render unless an all scope token is specified.

[shields-ci]

	Warnings
⚠️	This PR modified service code for circleci but not its test code. That's okay so long as it's refactoring existing code.

	Messages
📖	✨ Thanks for your contribution to Shields, @haythem!

Generated by 🚫 dangerJS

[paulmelnikow]

Fabulous, thank you!

Agreed the permissions issue should be documented until it's fixed. (#1064)

Would you like to add the documentation? If you put a documentation key in the badge examples containing HTML it'll render on the badge popup. Here's an example: https://github.com/badges/shields/blob/master/services/appveyor/appveyor-tests.service.js

[shields-deployment]

This pull request was merged to master branch. This change is now waiting for deployment, which will usually happen within a few days. Stay tuned by joining our #ops channel on Discord!

After deployment, changes are copied to gh-pages branch:

[haythem]

Thanks @paulmelnikow for merging the PR.

Would you like to add the documentation ?

Yeah, sure.