Bump omniauth-gitlab to 1.0.2 to fix incompatibility with omniauth-oauth2

As noted in gitlab-com/support-forum#1270, omniauth-gitlab fails if omniauth-oauth2 is bumped to 1.4.0, OAuth2 quietly fails due to https://github.com/linchus/omniauth-gitlab/issues/10:

```
21:26:04 rails-web.1             | I, [2016-11-07T21:26:04.245007 #56637]  INFO -- omniauth: (gitlab) Callback phase initiated.
21:26:05 rails-web.1             | E, [2016-11-07T21:26:05.068009 #56637] ERROR -- omniauth: (gitlab) Authentication failure! invalid_credentials: OAuth2::Error, invalid_grant: The provided authorization grant is invalid, expired, revoked, does not match the redirection URI used in the authorization request, or was issued to another client.
```

This was fixed and discussed here: 
* https://github.com/linchus/omniauth-gitlab/commit/26c47e55396205fab8439363c98136d0fde797f3
* https://github.com/linchus/omniauth-gitlab/issues/10

Bumping this version to 1.0.2 will ensure future compatibility.

See merge request !7348