Remove code responsible for showing team members

The code responsible for showing team members no longer works as
getting the collaborators list for a repository now requires the
request to be authenticated and the user (under which the token
was generated) to have push access to that repository.

e.g.: Trying to get the repository collaborators using a <token>
generated under an account without push access to the repository:

  $ curl -i -H 'Authorization: token <token>' \
    "https://api.github.com/repos/h5bp/html5-boilerplate/collaborators"

  HTTP/1.1 403 Forbidden
  Server: GitHub.com
  Date: Sun, 23 Nov 2014 21:20:12 GMT
  Content-Type: application/json; charset=utf-8
  Status: 403 Forbidden
  X-RateLimit-Limit: 5000
  X-RateLimit-Remaining: 4999
  X-RateLimit-Reset: 1416781212
  X-OAuth-Scopes: public_repo
  X-Accepted-OAuth-Scopes:
  X-GitHub-Media-Type: github.v3
  X-XSS-Protection: 1; mode=block
  X-Frame-Options: deny
  Content-Security-Policy: default-src 'none'
  Content-Length: 133
  Access-Control-Allow-Credentials: true
  Access-Control-Expose-Headers: ETag, Link, X-GitHub-OTP, X-RateLimit-Limit, X-RateLimit-Remaining, X-RateLimit-Reset, X-OAuth-Scopes, X-Accepted-OAuth-Scopes, X-Poll-Interval
  Access-Control-Allow-Origin: *
  X-GitHub-Request-Id: 592F527D:5F97:FED6B32:54724F8A
  Strict-Transport-Security: max-age=31536000; includeSubdomains; preload
  X-Content-Type-Options: nosniff

  {
    "message": "Must have push access to view repository collaborators.",
    "documentation_url": "https://developer.github.com/v3"
  }

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Ref: https://developer.github.com/v3/repos/collaborators/
Fix: h5bp/h5bp.github.io#18